Sharing three network

With the merger of Three/Vodafone does lebara switch to three if a better signal?, as I am reading conflicting stories that not all MVNOs of three/Vodafone do switch between?
Thanks

Myself I’d prefer Lebara switching to EE.

I doubt that will happen EE mnvno costs more and they would need to reissue sim cards to everyone again which adds costs.
Vodafone + three will be the biggest network once combined and with lots of investment coming should be great.