And just for the record, RTS buses do have bays beneath them... They just don't have floors in them. A very easy condition to fix.
My RTS had the same use as your MCI. It was called an intercity bus instead of an intracity bus. In my case, the bus was used to haul people from San Jose into San Francisco. This type of RTS had quite a few differences from the in-town models - highback reclining buckets was one (instead of hard blue plastic), and a righthand rotation 6V92 with 5-speed auto trans was another (vs lefthand rotation and a 3-speed). It also came with highway gears instead of city gears.
My bus is ex-GGT #1123. I was told that its route was San Jose to downtown SF. I don't really know their routes so it may have been different but it is one of those type of buses.