The Mass State PD Troop E (Mass Pike) operates on the 800 trunk system, as well as some of the older VHF-hi frequencies. This depends on which section of the pike you're trying to monitor. I believe that the VHF system is used more in the central and western parts of the pike, but I'm not sure of this. I think there has been a gradual switch over to 800. I can confirm that the eastern Pike troopers (at least East of the I95 tolls) are dispatched on the 800 system on tne E-PTL-1 talk group. You will hear activity on E-PTL-4, which are the troopers covering the major tunnels and the Mass-pike-93-big dig ops and details. I have yet to hear any activity on E-PTL-2 or E-PTL-3 even as far west as Amherst. As far as I know, you need to monitor both systems to cover the entire Pike. Operations in the Boston area are primarily on the 800mhz trunk system. You will hear ops on the VHF system, but dispatches are usually the roadside assistance "h.e.l.p." trucks and not cruisers, so don't confuse them when you hear dispatches to accidents and DMVs. Near Boston, the H.E.L.P trucks are dispatched on the VHF system, troopers on the 800. I believe in some areas further west they are both disptached on the VHF system, but I can't confirm this. Check out these links:
I hope this helps and happy scanning.