Are you talking about coming or going?
Flying in to Orlando, Magical Express is not intended to transport just the Guest's luggage. Any Disney resort Guest is eligible to use Magical Express and its luggage delivery feature (i.e. not either/or, but both).
Going home, anyone flying on a participating airline can check their luggage through to their home airport and check in for their flight at the Resort Airline Checkin counter at their resort - then use any mode of transportation to get themselves to the airport.
Any given Cast Member is well-versed in the area in which they work - for example, Dining CMs know, or should know, everything about dining reservations, restaurants, etc; room reservations CMs should know everything about room reservations.
To get the absolute, definitive answer on Magical Express, the Guest would need to call DME directly - there's a toll-free number on Disney's website, and in one or more 'sticky' threads on the Transportation board.