Gunsmithing Will Remage prefits work with a trued action?

It didn't work for me on a ptg trued action, I couldn't get the barrel centered so the scope needed all its wind age to be able to zero.

It worked on a standard action that I had, but I see remages not very positive anymore, getting a good barrel fitted is not much more expensive
 
Again, it depends.
If it was a full custom, then, as stated, no.
When he first started, he was offering an accuracy job, specifically for the SPS tacticals, he trued everything else up, but retained the factory barrel, so he only cleaned up the threads. If that is the case, then yes.