As promised, the ArcadeFire.com presale started at 10am this morning. It was too much for their servers to handle though... see above screenshot. Whether or not the NYC show was or is part of that presale... is sort of in question (now that the site it back up - I don't see it listed there).
That said, the above presale is not to be confused with the presales mentioned along with the NYC date ("Tickets for the NYC show go on AmEx presale June 9th, Fanclub presale June 10th and general sale on June 12th."). June 9th and 10th are presales that came with the NYC show information... which I assume are both Ticketmaster based (but maybe not)... and which were posted by me before the whole tour announcement... which included the news of the presale that started Wednesday at 10am.