You have a single branch with 3 workareas, but only want the DCT to work in one of the 3 ? Can the DCRs be visible in all other workareas ? Then you can accomplish this with permissions and submit.cfg.Otherwise it is really bad design.
If you do not want ot see anything of that template (i.e. not even see templatedata) in other workareas on the same branch, then you have a bad design
I will argue with you on that the option is to simply copy only relevant categories/data types to relevant workareas. And never do Get Latest on templatedata ...