Towers: Telus priority, Bell secondary
As Koodo is a Telus sub, I would expect that Koodo has the same PRL as Telus phones. That is, if there is a Telus signal in sight, even horribly weak, then it will use that one, even if there is a full strength Bell signal. Only when Telus drops off the map entirely will it roam to Bell.
Vice versa is true for Bell, and likely for their Solo sub. Virgin and PCMobile lease from Bell, so likely the same rings true for them.
The nutshell: If you want to know what your coverage would be like, get a friend with a Telus phone to try it out.