reannsfer? I'm not following, do you mean transfer? If that's the case, than no. Do you think ANY world leader will transfer their country at will? No.
in a gameplay aspect: it would make sense, if for example a main front were far away from one team player and he might wish to have a planet or asteroid closer to the action for a forward production, supply and repair centre. as such, one team member could conquer it or it could be an allied effort, but ownership can later be transferred to whoever can make the best use of that world. this problem of course only exists because only one player can construct structures at any one planet, but thats ok.
as for realism however abstract that is: for one, leaders give up territory if they have to, when faced with an overpowering opponent or following a military defeat. one could argue last weekends events as a distant example, other examples include various provinces gained or lost throughout the centuries, aka franco-german regions, northern italy, parts of china, etc. etc. and, sometimes, countries just swap territories for one another. I think germay gave away some african colony in favour of an island closer to her homeland. so, yeah, that happens to.
that was geeky now. in any case, giving away planets, be it for allied team operations or in the wake of an enforced cease-fire would be a welcome diplomatic addition imo.