If theres an empty company aircraft going to where the crew are needed, obviously that would be first choice (no cost). On occasion, I've managed to get crew onto a jumpseat with another carrier via an ops to ops call (to return the favour when required. My previous companies have all had interline agreements (preferential seat rates) with major airlines (and taxi / coach companies) so interline travel would be next choice (wether direct or with flight connections). Full fare tickets with lo-cost carriers are frequent (EZY / RYR etc). During ATC strikes we once even hired a coach with 2 drivers and popped a crew into Europe via the Channel Tunnel. Have positioned crews to pick up aircraft on Kingairs, PA31's, Citations (normally a twin engined aircraft)to avoid impacting the flying programme(sometimes delays can go on for days during peak periods)... even positioned an engineer and some spare parts on Challenger Jet (UK - Africa) because it was the quickest way.... as long as there is budgetary approval, anything is possible....
Duty time does have an impact... as long as the crew are well rested (normally a rest period equal to the duration of the journey ) it works out.