Settling in to routine at Red Hat now, and starting to get stuff done. Stumbled across a particularly nasty side affect of PIE and rpm's internal provides generator.
It turns out rpmbuild is adding Provides: basename(/path/to/pie/exec) to the package header. This in turn causes all EVR against that basename (often identical to the package name, or even worse for ppp created pppd which was conflicting with initscripts).
Fix is now in HEAD.