There is a variety of long weapons used and some of you would be surprised. The MP5 is still very popular and proven. Contrary to previous posts the RCMP is not shelving the MP5, far from it. Anyone who say's differently is not in the "know" and is speculating. The MP5 is limited in some ways and most teams have a combination of MP5's and 5.56mm carbines. A few Services have gone straight to 5.56mm weapons only. (Examples are; The Calgary Polcie Service and The Medicine Hat Police Service Tactical Units.)
The dominant weapon is the Colt Canada CQB or the C8. Outstanding weapon and very reliable. Armalites are still in use but have a terrible reputation and are hated by many Services. Three Services I know will never buy another Armalite and only purchase Colt Canada now.
HK G36's are used by quite a few and doing well with the primary complaints being the factory sights / scopes.
Swiss Arms / Sig is also in use by a few.
Old Colt M16's, Uzi's, Steyr Augs, Ruger AC556 and Mini 14's, HK 33's and HK 53's, just to name a few.
HK 416's are now also in use.
As stated before, Colt Canada has gone after the Canadian Police market very, very aggressively and attempted to under bid everyone. I'm sure they still make a profit but It's got to be slim with some of the prices they are offering.
There are some FN P90's in use as well (MUC in Quebec).
Rich
P.S. I wouldn't trade my issued Swiss Arms for any of the others and I've tried, carried, trained with and been issued quite a few.