it depends on how much they need you, if you are badly needed by them and they see no other options they can talk directly to your current employer and seek a release for you.... this is an buy-out situation and usually they can fix it in days time.

however if they encounter problems and they think they can get someone as good as you without going through this process i dont think they will do that...

your current employer has all the right not to release you if this is your question.