For years, the topic of allowing multiple accounts to manage a Google Place listing has been a hot and often requested feature.
The issue comes up often where someone claimed a listing but needs to transfer or also delegate permission for someone else to manage a business listing within Google Maps / Google Places.
Well, it might be coming soon - maybe?
A Google Places Help thread has Joel H. from Google said "We'd like to have a great interfacing for sharing listing between multiple accounts, but have no details to share yet."
Of course, Joel is not saying much here but he is alluding to it being a possibility in the future. How soon? I am not sure but we can be hopeful.
Forum discussion at Google Places Help.