We have a 24x system in one office and a 6x system in another. The 24x location is the primary site. There is a separate conference center in each. So if one person creates a conference, a second person in the other office can't get to it by dialing 408. The conference doesn't exist in the other office. Is there anyway to connect the two conference centers so that there is only one?

Just create an extension in the 6x that points to the conference center of the 24x. That extension will be you access code for the conference bridge on the 24x and u can still use the one on the 6x also.