As one who has done it (many, many times), an "ID00" is a "free ticket" but as "staff on duty", one can always be bumped if there is a fare-payer who wants the seat. unles you have a Flight Ops badge, and can con them that you are dead-heading and have to operate another flight
)
As an "old buggr", many (not avaiation-related) companies have offered me interviews and, if it was at an appreciable distance, they have been prepared to offer reasonable travelling expenses (same applied when I was interviewing others) - and I'm talking about train fares across UK, not "dodgy free" tickets that can leave you stranded in Singapore for 2 or 3 days!
As an ex BA (BOAC) employee, I'm sure "The Corporation" would not have acted like that in "The Old Days"
If you were to interview for Global Cheap Air, or Fly Euro Cut-Price, I might expect this, but not with The World's Favorite Airline.
AAAgh! - Maybe it's time they put me out to pasture - I'm a dino of the old days