I don't have any to test with, but I an attest that all other LGA 2011 systems I have come across that support v1 cpus support v2. It is possible however that the C6220 is different. Did you update all the nodes?I thought the same thing.. but after applying the BIOS 2.5.3 to a C6220 board, it was not able to POST with a v2 CPU, unfortunately.
I would love to be wrong about this, but it appears there is a reason that they came out with the updated C6220 II hardware.