Google is not party to the contract, so they have nothing to fear. You can not be sued over a violation of a contract that you are not a party to, that's just plain silly.
In fact, any number of google employees could have singed any number of NDAs with other companies without ever having disclosed those to google or being required to do so.
And google could never be sued for violating those contracts, tortious interference would be limited to those cases where google would force the employee to breach their NDAs, naturally limited to any confidential information that that employee might have (my guess: not much).
As long as that's not the case I really don't see why simply letting this guy have his 'status' could ever be a problem.
If microsoft wants to sue google I'm pretty sure it won't be over something as petty as that, and if they do it'll be a minor blip on googles legal bill and a bit of bad PR for microsoft.
Now it's significant bad PR for google, they come across as petty and paranoid.
You absolutely can be sued over a violation of a contract that you are not a party to.
One way is called interference. MSFT needs a reasonable expectency of a valid business relationship with the MVP. GOOG would have to know about the relationship between MSFT and the MSFT. MSFT would have to argue that GOOG intentionally interfered with the relationship with the MVP (such as by exploiting the MVP's NDA to get sensitive information about product plans), and then argue that GOOG's interference damaged MSFT.
I'm not a lawyer, but been at companies where things like this have happened over noncompetes and NDA's.
Obviously, if GOOG and the MVP do nothing to violate the NDA, nobody should get sued. Obviously, it is possible for the MVP to work at GOOG with any number of tricky relationships with MSFT. But saying "GOOG didn't sign the contract, so it could never (your word) be GOOG's problem" is a drastic oversimplification of the legal risk.
It would work slightly different (but that may be just to locality) here: MSFT would have to sue their MVP for breaking their NDA, they could then implicate that their employer forced them to, then their employer could get sued.
Alternatively, but this would be a completely roundabout route, Microsoft might get wind of google having access to inside information, with some proof, during discovery it would be found that it was leaked by the employee (with, for instance google acting in good faith since they could not know that this was internal MS information). The end of that one would probably be google being unable to use the 'tainted' information, and microsoft suing the MVP for breach of contract.
I think this latter scenario is what causes google to 'prefer' it if their employees would not have such contracts with third parties. It's a stretch, but it could happen. Best not to have even the possibility.
In fact, any number of google employees could have singed any number of NDAs with other companies without ever having disclosed those to google or being required to do so.
And google could never be sued for violating those contracts, tortious interference would be limited to those cases where google would force the employee to breach their NDAs, naturally limited to any confidential information that that employee might have (my guess: not much).
As long as that's not the case I really don't see why simply letting this guy have his 'status' could ever be a problem.
If microsoft wants to sue google I'm pretty sure it won't be over something as petty as that, and if they do it'll be a minor blip on googles legal bill and a bit of bad PR for microsoft.
Now it's significant bad PR for google, they come across as petty and paranoid.