Yep Bryce has always had refractive caustics - just crank up the refraction on a glass object and watch them pop. Erlik is spot on - it is the reflective caustics that it doesn't have and those are the kind that take special sampling algorithms beyond standard ray tracing. Vue has the same kind as Bryce - I think I even have old Bryce 1 renders somewhere that show these little caustics. I also think the HDRI is making them a little more prominent since it is such a refined quality of light.