My husband & I have gone on several organized rides. Toys for Tots here in Florida is huge! Sometimes, there's actually a few officers that will "escort". Typically those rides are kept off of interstates. I have no idea how things are done in other states but it would seem safer for the bikes to all stay in the left lane to me.
Here's a link that explains Motorcycle Parade safety:
All Things (Safety Oriented) Motorcycle - Group Riding Guidelines