on iOS 16.2 Beta 2 , the Carrier Bundles i get indicate that Yoodo now supports WiFi Calling on iPhone

Download IPSW and extract the Carrier Bundles inside

Not really separate, 40% of the network is already merged.
Many places Celcom and Digi uses same eNB now. Just path to core network is different.
CDG seems like tend to shut down Celcom towers and reuse Digi towers, so the network quality might drop. But merged towers provides very good speed (1+1/3+3/1+3+3+8/1+8/3+8) with 4x4 and 256QAM, able to achieve 200Mbps+ speed. (Max i got is 600+)

Me as a Digi users feels their coverage is somehow better than Celcom for residential area (Why? Because the residential area I usually go all Celcom mati before they merge with Digi)
Rural area of course Celcom wins , but so far for indoor I have no issue with Digi

Not to mention in my Kampung Digi have 1+3+7+8 CA (before merge) but Celcom only have 1+3 CA which resulting heavy congestion during CNY. Digi speed drop alots during peak time on CNY but at least still can scroll Tiktok / Youtube at 1080p, Celcom is totally dead, sending a WhatsApp text messages requires 1 minutes to send. (My cousin's TPG SG roaming on Celcom is basically unuseable, have to rely on Digi / Maxis and my own Celcom also dead at that time)

So I would say always have another alternative backup telco in Malaysia.
Im currently holding CDG,Maxis and U Mobile(Roaming) at the same time just to prevent one of the network not working.