I'd be surprised if there is any (significant) money in the BNYM account. The impact is mostly to limit the accounts that VZ can use to move money. It is essentially a forcing action to get VZ to settle.

It is one more necessary step but I doubt it is the endgame, which is likely to be the case over PDVSA et al.

The risk of opting in is that Gowling will necessarily cause delay and may (if they lose) cost all shareholders. It is possible (probable maybe) that there are sufficient shareholders opted in so that Gowling will act regardless of whether anyone else opts in so this risk is forced on all shareholders now. There is risk of not opting in if the court were to somehow favour the opt ins i.e. give these shareholders a bigger share than other shareholders. Something else to consider is if Gowling win a bigger payout then paying Gowling for this may be ethically better and only the opt ins are paying Gowling.

I think it boils down to a simple question. Do you believe Gowling can win? If yes then opting in may have merit, if no (or if you have no idea) then not opting in may make sense. It's important to distinguish between wanting Gowling to win and actually believing they can (because you have taken legal advice or have analysed what we know of their case) - we all agree on the former, the latter is where opt ins and opt outs are divided.