if an accident were to happen and a pedestrian was injured due to
tripping over the cart or something similar. Has anything like this ever
happened? Would they be left to deal with the situation entirely on
their own?
That's certainly what the WTS seems to want to happen. Utterly brazen. Especially as PL insurance for those sorts of activities would be a minimal cost.
I think what is more reprehensible is that the letter was only to the elders, not to the congregation. So those poor saps stood by the carts more than likely don't realise that the WTS will cut them loose if there happens to be a claim against them.