Phew--cross contamination nightmare at work. In my experience acetobacter in the same cabinet (and in same ventilated space of fermentations) is detrimental to the other ferments. Granted acetobacter is everywhere but it needs a way to innoculate and establish, and being in the same cabinet is all it will take.
The ginger beer with brett...will become just brett and it will eventually kill off the two organisms in true ginger beer plant (assuming you are using a real GBP, like yemoos.com or gingerbeerplant.net carry). And then the brett may contaminate ANY other ferment in the same ventilated space. Is there a particular reason you want to innoculate GBP with brett? (If your GBP is yeast + ginger, then I understand why you may want to add brett...but to real GBP?)
It may be better if you consider ditching everything in that cabinet and starting over with the vinegar the furthest away, like a garage or basement. Kombucha and GBP should be fine if you keep them a minimum of eight feet apart, but not in cabinets that connect and share same space. (I have fermented all three (no brett) with no issues, at the same time). Introducing brett....take it far, far away from kombucha and/or vinegar.
Motto: quel che sara sara