Celcom and Yoodo belongs to their parent company - Axiata. Its technically not MVNO unlike XOX , Tunetalk .
So here is my assumption. Network performance prioritize to both Celcom and Yoodo first followed by their MVNO partners.
But here is my experience with Umobile and maxis. Probably not the best scenario to compare but you be the judge. fyi there is no Umobile tower in Cameron (which is kinda odd and stupid for Umobile not investing network over there)
One time i was in Cameron for holidays. Brought along my Umobile and My hotlink flex.
sitting in my rented aapartment i could see Umobile trying to connect to Maxis on Hspa..but only lasted for a few mins only before the line auto downgrade to EDGE mode.
whereas my Hotlink stayed on Hspa permanently.
What does it tell me - Maxis doesnt want to share 3g / 4g signal at all with Umobile even with RAN agreement.
I have nothing against Celcom because im having Tunetalk also and looking fwd to ditch (port out) my ugly slow Umobile postpaid in exchange for either Yoodo or Digi Prepaid.
my area i stay now seems to have very good speed with Tunetalk but only concern with the massive subscribers porting out from Umobile to XOX (or any Mvno celcom brand)