The OP questioned the basic mechanics of how this system of free tickets on FR can work with the "assumption" that the positioning pilot was " additional or Sn " crew.. then muddied with briefings etc etc .. later the OP asked about the aspect of FTLs.
The thread has largely ignored the first point that FR crews, along with many others, can get free staff travel and just turn up at the gate, maybe the difference is that the FR crews don't get a ticket but I am sure they are LMC on the load sheet.. other airlines issue a blank boarding pass..
As pointed out, if you self position for your own needs it is not duty and the company doesn't give fig, neither do the authorities... on the other hand if the question is, is it sensible before a duty to position across Europe, and are you rested enough.. that's another topic and one that was well ventilated about BA long haul crews living abroad. Personally, I can get more rest tucked away in the aircraft with headphones under a blanket than I can get trundling around the M25 and can arrive " rested" .
Dont a fair chunk of NLH live abroad? Along with many others on commute contracts ? or are we now saying Joe Bloggs is going to position across Europe after and before each duty? The reason I say fellow pilots are " not interested" is not the topic but the implication that once again, a small benefit of the job may be eroded by some red tape rubber stamp Jonny in whitehall.
IF the company ask you to position on an " OFF DAY" it is no longer an off day and is duty.. full stop.. positioning AFTER a duty is usually not duty if it can be accomplished within the normal FDP. It only effects rest required.
So in the Nutshell, pilots that choose to live away from base for their own lifestyle needs and take advantage of free travel or un-ticketed travel do so under their own responsibility, how can we possibly hold airlines to account for this?
As for airports allowing access through crew channels, this is up to the guy on the gate at the time, yes he/she may be breaking the rules by doing a favour..
Lastly, I bet my bottom dollar that we have all at some time had the call " I know you are off...but can you do us a favour... etc etc" the cloth cuts both ways