Even though I did not witness the actual taming of the Ruby bunny, I did notice a sales thread via on #Trade channel today in regards of a Ruby bunny being up for sale (received a confirmed response reply by the seller as the Ruby bunny was tamed by him today). GZ Master Chief
Yes I did catch a ruby bunny and chief(my bf) posted on threads So I can personally say yes they do spawn but I definitely was wondering for quite some time. Good luck and keep trying!