Hi Mikael:

I touched on some of these issues earlier this week.

And if it's not refutable,how shall we interpret the Five Ways in the light of the B-theory?

Since causes in esse aren't temporally prior to their effects, pretty much the same as before. For example, as long as there are still potencies and causal relations, you can still argue that it's a necessary condition for there to be change that some potency be reduced to act. So, you can still defend the First Way. 

The other four Ways remain the same.