There is a lot of activity on MPSCS. However, depending on how you have your scanner configured, you may not hear anything. If you're configured to "scan" talk groups, and you don't have any talk groups programmed, then no, you won't hear anything. You would need to program some talk groups for your area, or instead of "scanning" talk groups, you would "search" talk groups, which would then find, and monitor any talk groups in your area.
You indicate that you have a BC796D. It should work in a simlar manner. Have you monitored MPSCS using it?