I have been trying to figure that out, as well. Was it a transfer away from June? Or a transfer away from Waterford? Would leaving give him access to greater resources that could allow June to escape to Canada? Remember, he said he had “info on Waterford” - presumably ratting on his Commander could yield a big promotion for him and with it, greater access to power and resources and greater opportunity for June to escape. Any other ideas?

I agree that him leaving could've been so that he'd have more chances to help June escape. I don't see how leaving her would be smart though. She's pregnant with (presumably) his child. Wouldn't he want to be able to keep an eye on her and keep Commander Fred away from her? Also, I was also wondering, where would he say he'd been when he was visiting June? How hasn't anyone figured out yet that he helped her?

Presumably, as an Eye - in addition to being “just a driver” - Nick has some freedom (as much as anyone in this society) and latitude to be able to run his own ops & surveillance. Under such a guise he was likely able to get the time off to help June.