pumouse is correct. Arrangements are normally made, just as they would be for any theatrical production, for understudies and stand-ins. In my experience, skaters (and actors) are usually trained on a rolling basis and are able to join the cast in any city as necessary. Rehearsals are held during the day to fuse this training with the particular chemistry of the continuing cast.
The details of this case are sketchy, so I hesitate to make a judgement call, but these two men should definitely have been suspended and the matter investigated both by the presiding law enforcement authorities and by an internal panel from Feld &/or Disney. Disney advertises for skaters ALL the time and I know several people who have joined a tour for a year or so before/after college. It is a great opportunity for young skaters and I hope this incident does not tarnish any innocents who may be involved.