LNIDA
I don't follow why it would be a difficult call for Titan (or any other ACMI company) pilots.
If such a scenario were to be played out, I doubt very much if the average e.g. Titan pilot would be aware of the fact that easyJet pilots were on strike in Lisbon.
All that would happen would be that the phone would ring and crewing would tell them to go an fly in Lisbon for a few days. And they would merrily go off and do just that.
The fact that a strike may be ongoing is irrelevant - in fact if an e.g. Titan pilot refused to go to cover such a series of flights, they may well be breaking the law as well. Who knows, but I wouldn't want to be a test case....
Let's hope the sorry mess gets cleared up before it reaches that stage anyway.