Assume an previously auto-accepted meeting room booking created by a normal user. Is it possible to give a different "room manager" user the right to change that existing booking to a different room, and automatically notify the attendees? This is a slightly different situation than the regular delegate setup where they receive the initial request and then approve or decline it from the start.

Yes, you can follow this way to do that. Give "room manager" full access permission to users' mailbox, then "room manager" can open room users' calendar, change the room (on previous meetings) and send the update. After that, attendees will receive updates for the meeting. Thanks, EvanEvan Liu TechNet Community Support

But any normal user can book a room. Using your solution, would the "Room manager" not need full access to everyone's mailbox? If so, that's not realistic. I have tried giving myself full rights to two test rooms, and manually moving a test meeting from one room to the other. But it actually makes a copy of the meeting in the new room, leaving the original meeting as is. There is also no notification sent out in regards to the new location after the copy. So it would appear Exchange 2007 simply has to process to do this easily.

Basically when you use room mailboxes to auto-Accept meetings, if you need those meetings to be moved to another room ( in short another room mailbox) you will need to have the user cancel the original meeting & send a new meeting. I would avoid making updates to meeting that you are not organizer of ..keeping the meetings clean is the best way to manage them.

But any normal user can book a room. Using your solution, would the "Room manager" not need full access to everyone's mailbox? If so, that's not realistic. I have tried giving myself full rights to two test rooms, and manually moving a test meeting from one room to the other. But it actually makes a copy of the meeting in the new room, leaving the original meeting as is. There is also no notification sent out in regards to the new location after the copy. So it would appear Exchange 2007 simply has to process to do this easily. Yes, it is not realistic to work on all the mailboxes. If your problem is based on all the users, I suggest you send email to the meeting organizer, ask him to change the room and update the meetings. The way you try to edit in room mailbox will not work, you need edit on organizer's calendar and send the updates. Thanks, Evan Evan Liu TechNet Community Support

Based on experiment, I found this to be the case. Thanks for the confirmation.