All the fluff I've read (Codex Grey Knights and Codex Daemons) says no. When you think about it, it makes sense.

Daemons can't break through to the materium except with help from someone already there (except in areas like the Eye of Terror, where the barriers are broken or extremely weak). Inside the warp, there's no way that another daemon (especially one that was about even with the banished daemon) would be able to reduce the banishment, since it was enacted with a level of power superior to what they could produce.

This leads me to believe that only direct intervention from a Chaos God would be able to pull it off. However, the only God that I could picture doing this is Nurgle. Khorne would be too angry with the banished daemon to help (and might even punish the offending daemon). Tzeentch would call it part of his master plan. Slaanesh would be too busy doing . . . . yeah, let's leave that blank. Nurgle cares about his followers, and if he weren't too busy, might be amenable to helping the daemon in exchange for some act of servitude.

Another quick question:
Primarchs in the background were always shown as being stronger than Greater Daemons (Fulgrim defeating an Avatar of Khaine (even if he DID get his but handed to him), Sanguinius defeating Khabanda during the siege of Terra). Would this mean that the Chaos Primarchs elevated to greater daemons would be the premier servants of the Chaos Gods (purely in terms of power level)?