The customer system has about 50 station in the "all page" group. There are three OAS cards in the system for a total of 48 MGI channels and they are using SIP trunks.

I also see the same behavior on my little 7100 test system here at the office which has 15 IP extensions (all in one page group) and only 4 MGI channels. It also uses SIP trunks.

I'm hoping to be able to do some additional testing on a system with analog trunks.