I have a customer that is running CM 4.1. Their carrier would like to do SIP trunks to the remote sites. Is a VGW running CUBE capable of terminating SIP with CM 4.1? How does the CM side of the VGW look, like an H323 or MGCP GW?
You're thinking of something different. I think SIP CME may have required authentication, but certainly not CUBE.
All you need to understand is that SIP and H323 are open standards. CUBE supports SIP and H323 and can connect (theoretically) any two SIP and H323 endpoints that are also in specification.
Some of the things you may need to take in consideration is that CCM 4.x SIP trunks require an MTP, but outside of some of the CCM restrictions you should not have any problems. That is not to say, that CCM does not have SIP problems. But it wouldn't be a CUBE issue. Since CCM 4.x is a fairly close to the point where we introduced SIP, I would be cautious about SIP use in those versions. Everything should work, but there may be some minor issues that are fixed into CUCM 5/6/7.
already addressed with the PDI case you opened