Is the OS7200 ver 4.7 able to work with the MGI64 card? I want to create a switch for my client who has 30 sites running Samsung IPPBXs and only one with Avaya. The switch will have 2 Tepri cards and 3 x MGI16 or 1 X MGI64. SIP peering would have been easier but the client's AVAYA operator is not local.

No, the os7200 does not support the mgi64 card or the tepri2 card.
If you have ip handsets your better off with oas cards over the mgi16