Re. the tomato...
Well, it should be pretty easy to tell. Is the new little plant growing from the old plant, assuming it was not removed from the pot? If so, then it survived the winter outdoors... which is extremely unlikely in your/our climate. (Note: Tomatoes are perennial plants but only act as such in much warmer climates.) More likely, if is actually a tomato, it is a seedling from a seed from a fruit that rotted on the plant and fell into the pot.

It is more than likely a tomato plant. The year my son was born I was put on bedrest and could not get to "cleaning up" my vegetable bed and the following year I have tons or tomato plants. So many I had to put them out like bad weeds!

A volunteer tomato, I bet! And being an heirloom variety, it should be true to form, meaning identical to the Brandywine you had in the pot last year. My nephew's tomatoes are prennial in Phoenix but I've never heard of one surviving a Minnesota winter. If it were coming back from last year's plant, it would have a thick knarly stem and root going down into the dirt. If the stem is delicate down at the bottom, it would be a tender new plant.