I don't know of any efforts to make them work across CMP in tmm-land, but that's hardly definitive. The general way that stats are handled right now is that each tmm keeps track of its own statistics, and then these are published to user-space where they are rolled-up (external to tmm). So it is quite possible that SNMP reporting works as expected, even if each tmm acts independently. This is not a part of the product that I'm intimately familiar with, so please don't take this as gospel.
That said, we do recognize that there is a need to accumulate and access statistics across processors entirely in iRules, and are actively working on this for a future release.
Nimbostratus