Sources close to the process suggest a request for proposal (RFP) went out to seven firms last Tuesday (13 November) and interested parties had until Wednesday (21 November) to make their submissions.
Alongside ITV, Channel 4, Channel 5 and BSkyB's ad sales arm Sky Media, the other companies invited to pitch are understood to include the Jeremy Lawrence-fronted Axiom Media, Dolphin TV and John De Napoli's Mean Broadcast.
Industry sources suggest four sales houses will be invited to present to BT next Thursday, 29 November, and BT executives hope to make a decision on the winning sales house before Christmas.
A spokesman for BT said: "Yes, we can confirm we've put out an RFI [request for information] with regard to selling ads on the new BT sports channel and we'll update when we have any developments to report."
Since making its surprise swoop for Barclays Premier League rights, paying £246m a year for 38 matches a season, BT has also picked up Premiership and England rugby rights and European football.
BT plans to sell its sport channels to customers watching TV through satellite platforms, but could also wholesale them to Sky for it to sell on as well, if the two companies are able to agree a commercially favourable deal.
Sources suggest ITV was initially the front runner for BT's production contract, but it pulled out of the process. BT is expected to announce the winning production company before the end of this year.
Spokesmen for Sky, Channel 4 and Channel 5 declined to comment. Spokespeople for ITV, Axiom, Dolphin TV and Mean Broadcast had not responded to requests for comment by the time of publication.