Here is a network that can host floating IPs:
+---------------------------+----------------------------------------------------------------------------+
| Field                     | Value                                                                      |
+---------------------------+----------------------------------------------------------------------------+
| admin_state_up            | UP                                                                         |
| availability_zone_hints   |                                                                            |
| availability_zones        |                                                                            |
| created_at                | None                                                                       |
| description               | None                                                                       |
| dns_domain                | None                                                                       |
| id                        | e48bdd06-cc3e-46e1-b7ea-64af43c74ef8                                       |
| ipv4_address_scope        | None                                                                       |
| ipv6_address_scope        | None                                                                       |
| is_default                | False                                                                      |
| is_vlan_transparent       | None                                                                       |
| mtu                       | 0                                                                          |
| name                      | melbourne                                                                  |
| port_security_enabled     | False                                                                      |
| project_id                | 1                                                                          |
| provider:network_type     | None                                                                       |
| provider:physical_network | None                                                                       |
| provider:segmentation_id  | None                                                                       |
| qos_policy_id             | None                                                                       |
| revision_number           | 3                                                                          |
| router:external           | External                                                                   |
| segments                  | None                                                                       |
| shared                    | True                                                                       |
| status                    | ACTIVE                                                                     |
| subnets                   | 0f7520e4-1777-468a-9047-0a87a13e178a, b4771a97-bfb8-4e48-89af-10cf88e63a7f |
| tags                      |                                                                            |
| updated_at                | None                                                                       |
+---------------------------+----------------------------------------------------------------------------+

Here is one that can't:
+---------------------------+--------------------------------------+
| Field                     | Value                                |
+---------------------------+--------------------------------------+
| admin_state_up            | UP                                   |
| availability_zone_hints   |                                      |
| availability_zones        | nova                                 |
| created_at                | None                                 |
| description               | None                                 |
| dns_domain                | None                                 |
| id                        | 56c84852-e8b1-49f7-be67-bc0cfaec4188 |
| ipv4_address_scope        | None                                 |
| ipv6_address_scope        | None                                 |
| is_default                | False                                |
| is_vlan_transparent       | None                                 |
| mtu                       | 1500                                 |
| name                      | sydney-02                            |
| port_security_enabled     | False                                |
| project_id                | 1                                    |
| provider:network_type     | None                                 |
| provider:physical_network | None                                 |
| provider:segmentation_id  | None                                 |
| qos_policy_id             | None                                 |
| revision_number           | 0                                    |
| router:external           | External                             |
| segments                  | None                                 |
| shared                    | True                                 |
| status                    | ACTIVE                               |
| subnets                   | 67ab51f2-d046-42b1-9197-2b1d8ed2c5a7 |
| tags                      |                                      |
| updated_at                | None                                 |
+---------------------------+--------------------------------------+

As an API user there is no way to tell the difference.