Not even close, masonb. Departments just plain won't make a knee-jerk reaction like that. As brechtd alluded to, there are costs to this for a department not already set up to run encryption. These aren't nickels and dimes, either.
Besides, it was the RCMP who were involved in the bus incident, not WPS.
RCMP on the new Alberta provincial system are going to be somewhere between partial and full-time encryption as well - either their special services will be full-time encryption, all channels will have selectable encryptability, or everything will be encrypted by default. This is just the new reality we live in, and its roots lie in September 11, 2001, or even earlier than that.
Just for the sake of a competing viewpoint, let me contribute this too: There is a community near me where everybody (and this is no exaggeration) has a scanner and listens to the RCMP. And the RCMP take advantage of that on a daily basis. It's not uncommon to hear an officer come on the radio and say "If anybody out there knows where Billy (name) is, tell him his horses are loose on Highway 1A again". So there are RCMP and others out there that acknowledge scanners are listening, and use it to their benefit.
IMO, the solution should be to have select encrypted channels for truly sensitive communications - tactical comms (for safety's sake), records/wants checks, etc., and the stuff that the FOIPP laws protect. I do find myself disappointed if police agencies (and others) choose to go full encryption to keep even the everyday patrol comms under wraps. I'm not one of those who says that it's my civil right to monitor the police, or that we deserve to hear what our taxes pay for etc. I just think it's a waste of money and resources to encrypt things like "Anyone up for Tango Hotel?" or "Request that you attend 123 Main St for a noise complaint - neighbor says that the occupant has been running his motor boat in the backyard for the past hour".