Me too, I can't wait to see PS2 versions of the ES buggies! Hope the Harasser makes a return as well (Wouldn't really be necessary though)
I'd wager that it'll probably be paid expansions, or even buggies only available to premium customers.
They already mentioned they aren't interested in going that route. Expansions/buggies are aimed to be free. I wouldn't expect them for at least a couple of months, but I'm very excited to see them.
Going by their current design strategies, wouldn't buggies just be flashes with a second passenger seat?