Can't your tech lead suggest that he'll do the release under the condition that someone from that other team pairs with him so that they learn how to do it?
Yeah, at a previous job, I had inherited responsibility for maintaining a particular poorly tested (and hard to test—lots of API dependencies), widely-used library. Most changes were contributed by users and I managed by reviewing new code and tests as carefully as I could.
At one point, one particularly hard-pressed user wanted to make really sweeping changes to the library and had limited time. I stalled and stalled to try and review all their changes and convince myself they were going to work, and they got more and more agitated, and my TL (who was himself frustrated by how much of my time this was consuming) told them "you can merge whatever you want if you take over maintaining it". So that's what happened, and everybody left happy.
