>unless they actually signed something along the lines "we will take responsibility if antitrust throws the deal away" but that would be quite unlikely in such a high profile transaction.
This is absolutely standard in M/A. Part of the risk of accepting an acquisition offer is that you're essentially putting your company's strategic future on hold, and if what you're doing that for falls through for any reason (including regulatory oversight) you want compensation for at least some of the lost time. Specifically, you won't even sign the acquisition contract without such a guarantee; the only real question is price.
This is absolutely standard in M/A. Part of the risk of accepting an acquisition offer is that you're essentially putting your company's strategic future on hold, and if what you're doing that for falls through for any reason (including regulatory oversight) you want compensation for at least some of the lost time. Specifically, you won't even sign the acquisition contract without such a guarantee; the only real question is price.