General Motors bought 3 SAAB 2000's to replace their 4 Convair 580's back in 1995. At the time GM owned Allison, which powers both the SAAB 2000 and the Citation X, so this was the logical replacement for GM's 580's and the Citation X's that replaced their Citation VI's. Shortly after GM sold Delco, the shuttle business ended and the SAABs were put up for sale but they have not been able to find any buyers. Roger Penske either bought or leased one SAAB and it's used for his NASCAR racing team, otherwise the other 2 just basically sit in Detroit.
As for Proair deal, GM was to supply Proair with their SAAB's but there was an issue with the FAA regarding these SAAB's being the first ones entering airline service and the expense of certifing them (maybe someone could explain what's involved in bring a new type into 121 service) so the deal fell through.