They knew they had no chance of survival before the prison uprising. Afghanis hold a bitter resentment towards foreign invaders, and that's exactly how those fighters were seen. Well before the prison uprising, the foreign fighters were said to be executing Afghan Taliban members who wanted to cross over to the NA. There is no love lost between the foreign Taliban and the NA. The NA took the opportunity to settle some old scores and did it with a vengence, as is their custom.

It seems reasonable to consider that those foreign fighters never really intended to surrender. It's quite possible they intended up mount that uprising all along simply because they knew it was the best way to kill as many of the NA as possible.

It's unlikely any of the remaining foreign Taliban members will surrender, but that has been obvious for some weeks now. Stratfor has a tendancy to either take a pessimistic (and often inaccurate) view or to state the obvious. Here's an example from a month ago. Compare their predictions to what actually happened. Of course, this isn't the only gloomy prediction proved wrong be events.