While working on the Protocol interface (Bug #20774) I was surprised to find that the Connection.Status and Connection.Interfaces properties still don't exist.
telepathy-glib branch, which shouldn't be merged until that spec branch is released and this branch is synched with it:
Running an unmodified telepathy-gabble with the patched telepathy-glib correctly gives it the Status and Interfaces properties.
wjt says review+, when Status gets a tp:added annotation that explains fallback to GetStatus.
Fixed in master for 0.19.2