I don't know for this for certain but if I'm remembering correctly the Bloc always had official party policy that they wouldn't form a government in the Canadian legislature if such an opportunity arose - when they became Official Opposition IOTL in the aftermath of 1993 Bouchard famously...
According to this, RPR and UDF already had agreed on fielding a joint candidate and beginning merger talks by early 2001 and the UMP was formally agreed upon months before the assassination attempt on Chirac took place.