Carroll approached club bosses last month with the offer, who have since contacted the NRL with a contract registration request.
If registered before tommorrow’s cut off date Carroll would be immediately available for selection.
“Tonie approached us a month ago in the knowledge we had a few injuries and we were coming into the Origin period,” said Broncos’ chief executive Bruno Cullen.
“It was suggested we wouldn’t consider taking him on until he presented himself in a state that proved he was fair dinkum about a comeback.
“That meant training, and training that had to be done away from the club.
“That purely means he would be eligible to play. Whether he actually does play or not will be up to the coaching staff.”
Carroll, now 33, played 216 first grade games for the Broncos – scoring 58 tries – before retiring at the end of the 2008 season.