recently, I've seen some changes in the mobile network codes (MNC).
Originally Videotron MNC was 500.
Later on, 510 appeared somewhere (maybe when they officially lauched their own network).
Recently I've seen 520.
This is mainly all on 3G
on my device when connected on LTE, MNC is always 720 (Rogers).
I've seen some 510 on LTE when LTE was first launched... but now all I see is 720 no matter where I am.
This is on an iPhone X on IOS 12 beta.
so it appears that Videotron is somewhat working on their network... and this might be causing problems for some users.
Hopefully this will be resolved soon for those that are having problems (it's fine for me... worked fine this past weekend when I was connected PRTNR 2 network in Réserve faunique du Saint-Maurice.
the most recent Operator config might fix a few problems here and there on iPhones. I guess it will be available with the next iOS version.
If you want to try it on your iPhone, upgrade to the iOS 12 beta (it's very stable on my device). all details on beta.apple.com... if you need help, you can contact me directly.