Striker Austin has rejoined Rangers, for whom he scored 48 goals in 89 appearances between 2013 and 2016, on loan from West Brom.
Warburton is set to pitch the 31-year-old straight in at Luton in Tuesday night's rearranged clash.
"Charlie is quality, he's well known at the club and he's a proven goalscorer," Warburton told the club website.
"He'll help us on the pitch and off the pitch as well in mentoring the young strikers, and he wants to do that.
"It's healthy competition for places and I have no doubt he will have an impact on and off the pitch. Charlie will be in the squad for tomorrow night, all being well."