I ended up being in Logan this morning longer than expected, so I was poking around Terminal C looking for some vegan friendly food, without much hope for anything better than trail mix.
Turns out the Boston Back Bay Cafe (kind of by Gate C15) carries some of the "Macro and Vegetarian" prepackaged stuff. They had the Vegan Pad Thai, Vegan Dumplings, and Vegan Udon Noodles. Supposedly they can be eaten hot or cold. I've had their stuff before and it's not my favorite, but in the airport, I'll take it.
Unsurprisingly, the cashier didn't know how to ring them up.