Have not asked the question that way, but I would think that in that case, your scenario of it being considered a concurrent stock sale would hold true and AIS would get their percentage of premium.
If I were a lawyer working for AIS, I would argue that a buyout of BPAX necessarily contains an implicit license transaction and hence AIS should be paid accordingly. This sounds like a case that could end up in arbitration.
“The efficient-market hypothesis may be the foremost piece of B.S. ever promulgated in any area of human knowledge!”