Based upon dialogue earlier in the episode I took it that the red zones shown on the star map, and later on screen, were the overlapping sensor nets extending from the mines that would make them explode. So yes, no triggering the Omega. Nus is daring the Federation to cross the line and make things explode, knowing that they will not since they value life and the fabric of space, unlike him.
Agreed that they should have given a bit more explanation on how Omega (artificial or otherwise) was in Federation possession. Since we know from Voyager that there used to be a standing order to destroy it.
Cheers