Oh, you can indeed find canned San Marzano's anywhere, though many (if not most) sold in the US are fake (but probably the same species): https://www.yahoo.com/lifestyle/san-marzano-tomatoes-probabl...

My point is that along the west coast, passionate pizzerias have more direct access to tomato growers, and might just be using fresh tomatoes rather than canned tomatoes. It's pretty safe to say that along the east coast, most tomatoes are going to be canned, so they'll be easier to spot.