Indeed.
I can tell you one thing though, a normal transit bus is not structurally safe enough to ever be allowed to operate on CN tracks along side other trains.
There are systems however, guided busways in use in some parts of the world, basically a normal bus with guide wheels and tracks - not steel rail tracks. Check out the
O-Bahn Busway in Adelaide, Australia.
Probably not practical for Halifax.. but interesting none the less. Would allow the buses to run on regular city streets downtown, but have its own private ROW off of the peninsula.