Could be...They look like it. They are the right size and all that. But there are a lot of barred birds...it is a color, and Plymouth Rock is the breed...They look heavy like rocks though. So you would be reasonably safe in assuming they are barred rocks.
My eyes aren't good enough to see if their combs are single combs or rose combs.
Since hatcheries have criss-crossed the Barred Rocks and Dominiques, that's about the only different in them, as far as hatchery stock goes. They sell the single combs as Barred Rocks and the rose combs as Doms. They are supposed to be quite different, but ....... that's just how it is.