Well ,to date if you wanted bullhead rail , the options were C&L and SMP. Historically these have been thin ( 0.6mm) sleepered track, which has been quite fiddly to lay and has very little strength. matching this with home built points, which were typically copper clad, still left things out visually.
Now C&L has released 1 metre thick sleepered flexi, using its exactoscale fast track bases as a basis is for this track. Its pricey at £6.50 ( with their enhanced nickel quality rail ) This is a great looking flexi. Also there are /were strong rumours that DCC concepts was/is about to release a RTL 00 track work , to UK bull head outlines.
as a result of this , I suspect PECO have moved to release a 00 scaled track as opposed to their existing H0 scaled track. Since code 75 PECO has been around for a long time, I dont think the timing has anything to do with wheel flange depth, its is notable however that the profile of the " chair" in the new 00 PECO track has the inside rail clamp, reduced down to ensure the pizza cutter wheels can still run