I've done some further investigation into this issue.
maverick exhibits the same symptoms as lucid; i.e. if the 127.0.0.1 address is not bound ntp exits on startup.
natty appears to deal with this scenario OK; removing 127.0.0.1 in a post-up step does not impact ntp.
Looks like this issue was fixed in the transition from v4.2.4 to v4.2.6 (possibly as part of 4.2.5p219)
I've done some further investigation into this issue.
maverick exhibits the same symptoms as lucid; i.e. if the 127.0.0.1 address is not bound ntp exits on startup.
natty appears to deal with this scenario OK; removing 127.0.0.1 in a post-up step does not impact ntp.
Looks like this issue was fixed in the transition from v4.2.4 to v4.2.6 (possibly as part of 4.2.5p219)