Some context here. Region of Waterloo actually owns the spur that's runs to Elmira while CN/GEXR is allowed to serve customers it has on that line (Chemtura). Since the Region owns the track, they can dictate when freight is allowed to go through.
CP by comparison is incredibly hostile to any other users on its track (see: Milton/Cambridge 3-track GO expansion requirements) CP's track is also heavily used by Toyota, and will continue to be for the foreseeable future. There will be no track sharing agreements between CP and ION along the Speed River. If ION is going to use the CP spur north of Eagle St, it will likely require buyout.
CP by comparison is incredibly hostile to any other users on its track (see: Milton/Cambridge 3-track GO expansion requirements) CP's track is also heavily used by Toyota, and will continue to be for the foreseeable future. There will be no track sharing agreements between CP and ION along the Speed River. If ION is going to use the CP spur north of Eagle St, it will likely require buyout.