Not that I know of. Many houses also have specialized in-house renders for voxels and occasionally, fluids.
Hella cool! Who is rolling their own outside of Weta?
DD? Animal Logic? Double Negative? Blue Sky is super proprietary, I'm curious what they are up to...
But more studios have their own full renderers these days:
Weta has Manuka
Disney has Hyperion
Animal Logic has Glimpse
Framestore has Van Damme
Sony has their fork of Arnold