Can an alert be MI if the opponents don't ask?
This is a situation that was discussed on Usenet recently, inconclusively. The situation arose under ACBL rules but I don't think EBU rules would be any different in this situation.
The bidding went P, P, 2!, X; 2, AP. 2 was alerted, but the opponents didn't ask what it meant.
It turned out that the opponents assumed (without asking) that an alerted 2 would be Flannery (apparently the only common meanings in that club are Flannery and a weak two in diamonds). The 2 bidder thought the bid was a weak two, their partner that it was Flannery. The defending side ended up missing a game in hearts that was bid by every other pair.
There was a UI issue here that needs addressing (a nonforcing 2 over a natural 2 is alertable under ACBL rules, so it looks a lot like the opener took advantage of UI to pass the 2 bid). However, I'm interested in what would happen if the 2 bid were nonforcing and nonalertable (it isn't alertable in the EBU because it was made by a passed hand), and no UI existed; is the incorrect alert misinformation if it isn't asked about? There seem to be two main viewpoints on the subject, "a weak-two 2 is announceable (not alertable) and thus alerting it is misinformation", versus "there are plenty of alertable meanings for 2 that look very similar to the weak-two bid, so the opponents assume a specific meaning at their own risk".
For what it's worth, I'm more inclined to the second view here: for example, "I can't remember whether we play 2 as a weak two or as Flannery" is an alertable agreement (possibly even the actual agreement in this case!), and yet the 2 bidder's actual hand is a strong possibility in that case. It's enough of a corner case that I think it's worth discussing, though.
(This, is, of course, yet another reason to always ask when a bid is alerted!)