No idea, but I think you mean
en masse, not in mass

Ah, right. Indeed. As I typed it I thought to myself, "This is one of those weird things that isn't spelled at all how you think it would be, isn't it?" And alas, I thought right but did wrong.

Not that I know of AV. But I'm trying to record a scratch track of voice as I do my dialog, and going ahead and creating the lip file at that time. I will have to replace the scratch track track for the final version when I have them ready, and I'm keeping my fingers crossed they will work together. Might be worth a try for you at least.
At any rate, I'm just glad we're able to generate them in the info dialog as opposed to the old way that should be lost for all eternity!
I think it uses the soundwaves of the file to time it as well. I notice that it always seems to pause the lips perfectly in synch with my voice actor no matter what. So I think if there is 3 seconds of silence in a clip, and a period occurs at the same time, it figures it out. That said, I'm not sure if your old lip will work with your new files. It just may not synch up well. Then again, this is all speculation.

And indeed. Praise be the divines that we don't have to do that horrid old method! It took me like 6 hours to do 200 lines for Deimos. I just did the first 30 or so for my mod, and it took like 60 seconds. That's 1 every 2 seconds, much better than the 12 in 5 minutes I could do before!