155.73 is licensed to Crossfield Fire in a simplex fashion. 155.7 is a tac channel, but most often scrambled (with a loud hissing noise followed by a short, quiet, very high pitched tone).
It's possible that the RCMP may have one of their repeaters on Broadcast Hill somewhere - and if you were at 17 x 85, that may have been what you were getting, just washing out your receiver on many (all) channels.