It's usually sufficient to meet the spirit of the specs if you can't meet the letter of them. So for instance a proposal to do the initial build in the Second Life main grid, with the intent of moving it to a behind-the-firewall SL instance at some point before the high security is required, might well be acceptable.

(Note that I have no specific knowledge about this request for tenders, or about any specific possible tender; I'm just speaking generally from prior experience with vaguely-similar things. And that was the US government rather than NATO, although I would guess that they're rather similar in this respect.)