I am seeing a similar issue, however the tables are all InnoDB.

ubuntu@server:~$ python -m neutron.db.migration.migrate_to_ml2 openvswitch mysql://USER:PASSWORD@10.251.1.8/neutron
Traceback (most recent call last):
  File "/usr/lib/python2.7/runpy.py", line 162, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/usr/lib/python2.7/runpy.py", line 72, in _run_code
    exec code in run_globals
  File "/usr/lib/python2.7/dist-packages/neutron/db/migration/migrate_to_ml2.py", line 462, in <module>
    main()
  File "/usr/lib/python2.7/dist-packages/neutron/db/migration/migrate_to_ml2.py", line 458, in main
    args.vxlan_udp_port)
  File "/usr/lib/python2.7/dist-packages/neutron/db/migration/migrate_to_ml2.py", line 138, in __call__
    metadata.create_all(engine)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/schema.py", line 2848, in create_all
    tables=tables)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 1479, in _run_visitor
    conn._run_visitor(visitorcallable, element, **kwargs)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 1122, in _run_visitor
    **kwargs).traverse_single(element)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/sql/visitors.py", line 122, in traverse_single
    return meth(obj, **kw)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/ddl.py", line 70, in visit_metadata
    self.traverse_single(table, create_ok=True)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/sql/visitors.py", line 122, in traverse_single
    return meth(obj, **kw)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/ddl.py", line 89, in visit_table
    self.connection.execute(schema.CreateTable(table))
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 662, in execute
    params)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 720, in _execute_ddl
    compiled
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 874, in _execute_context
    context)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 1024, in _handle_dbapi_exception
    exc_info
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/util/compat.py", line 196, in raise_from_cause
    reraise(type(exception), exception, tb=exc_tb)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/base.py", line 867, in _execute_context
    context)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/engine/default.py", line 324, in do_execute
    cursor.execute(statement, parameters)
  File "/usr/lib/python2.7/dist-packages/MySQLdb/cursors.py", line 174, in execute
    self.errorhandler(self, exc, value)
  File "/usr/lib/python2.7/dist-packages/MySQLdb/connections.py", line 36, in defaulterrorhandler
    raise errorclass, errorvalue
sqlalchemy.exc.OperationalError: (OperationalError) (1005, "Can't create table 'neutron.ml2_network_segments' (errno: 150)") '\nCREATE TABLE ml2_network_segments (\n\tid VARCHAR(36) NOT NULL, \n\tnetwork_id VARCHAR(36) NOT NULL, \n\tnetwork_type VARCHAR(32) NOT NULL, \n\tphysical_network VARCHAR(64), \n\tsegmentation_id INTEGER, \n\tPRIMARY KEY (id), \n\tFOREIGN KEY(network_id) REFERENCES networks (id) ON DELETE CASCADE\n)\n\n' ()


ubuntu@server:~$ mysql -u root
Welcome to the MySQL monitor.  Commands end with ; or \g.
Your MySQL connection id is 5215
Server version: 5.5.34 MySQL Community Server (GPL), wsrep_25.9.r3928

Copyright (c) 2000, 2014, Oracle and/or its affiliates. All rights reserved.

Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.

Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.

mysql> use neutron;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> show tables;
+------------------------------+
| Tables_in_neutron            |
+------------------------------+
| agents                       |
| alembic_version              |
| allowedaddresspairs          |
| arista_provisioned_nets      |
| arista_provisioned_tenants   |
| arista_provisioned_vms       |
| cisco_ml2_credentials        |
| cisco_ml2_nexusport_bindings |
| dnsnameservers               |
| externalnetworks             |
| extradhcpopts                |
| floatingips                  |
| ipallocationpools            |
| ipallocations                |
| ipavailabilityranges         |
| ml2_flat_allocations         |
| ml2_gre_allocations          |
| ml2_gre_endpoints            |
| ml2_vlan_allocations         |
| ml2_vxlan_allocations        |
| ml2_vxlan_endpoints          |
| networkdhcpagentbindings     |
| networks                     |
| ovs_network_bindings         |
| ovs_tunnel_allocations       |
| ovs_tunnel_endpoints         |
| ovs_vlan_allocations         |
| portbindingports             |
| ports                        |
| quotas                       |
| routerl3agentbindings        |
| routerroutes                 |
| routers                      |
| securitygroupportbindings    |
| securitygrouprules           |
| securitygroups               |
| subnetroutes                 |
| subnets                      |
+------------------------------+
38 rows in set (0.00 sec)

mysql> select * from networks;
+----------------------------------+--------------------------------------+--------------+--------+----------------+--------+
| tenant_id                        | id                                   | name         | status | admin_state_up | shared |
+----------------------------------+--------------------------------------+--------------+--------+----------------+--------+
| d8d6413cc57f4699aa539eb9de6f64de | bee5ef99-5414-49ad-a423-0b57a8244460 | Public_AGILE | ACTIVE |              1 |      0 |
+----------------------------------+--------------------------------------+--------------+--------+----------------+--------+
1 row in set (0.00 sec)


mysql> SHOW INNODB STATUS;
------------------------
LATEST FOREIGN KEY ERROR
------------------------
140701 15:30:04 Error in foreign key constraint of table neutron/ml2_network_segments:
FOREIGN KEY(network_id) REFERENCES networks (id) ON DELETE CASCADE):
Cannot find an index in the referenced table where the
referenced columns appear as the first columns, or column types
in the table and the referenced table do not match for constraint.
Note that the internal storage type of ENUM and SET changed in
tables created with >= InnoDB-4.1.12, and such columns in old tables
cannot be referenced by such columns in new tables.
See http://dev.mysql.com/doc/refman/5.5/en/innodb-foreign-key-constraints.html
for correct foreign key definition.



mysql> show create table networks;
+----------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table    | Create Table                                                                                                                                                                                                                                                                                                         |
+----------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| networks | CREATE TABLE `networks` (
  `tenant_id` varchar(255) DEFAULT NULL,
  `id` varchar(36) NOT NULL,
  `name` varchar(255) DEFAULT NULL,
  `status` varchar(16) DEFAULT NULL,
  `admin_state_up` tinyint(1) DEFAULT NULL,
  `shared` tinyint(1) DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
+----------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)