Our team has bought into TDD and wants to give it a go. Won’t other teams that aren’t interested in TDD nullify our efforts?

Most likely no. It feels tempting to call classic and mockist TDD “micro design techniques”, i.e. techniques that affect the design of small program elements like classes, modules, or clusters thereof. They will have impact on individual developers’ output and code structure, and such code will look and feel different from the untestable kind, but both kinds of code can coexist in the same codebase.

As long as there’s some CI server running the tests, and as long as other teams don’t delete your team’s tests or break them, you should be fine.