According to Fred Mitchell in the Tribune, the Cubs will retire Andre's #8 if he goes into the Hall of Fame as a Cub. But:
No word on whether the Cubs would follow through with retiring his number if Dawson is inducted as an Expo.
There were some players -- notably Wade Boggs -- who had been promised money for going into the Hall wearing the cap of a certain team (in the case of Boggs, the then Devil Rays, which was one of the reasons the Hall took the choice back from the player).
In this case, there's no money changing hands -- at least as far as we know. Frankly, the Hall ought to realize that there's a lot of money to be made for the Hall of Fame if they induct Dawson as a Cub.
It appears to me that Dawson probably has expressed the desire to go in as a Cub, but the Hall is balking. Dawson had his best years in Montreal -- save his one MVP season in 1987 in Chicago -- but arguably his greatest "fame" came as a Cub. We await developments.