Actually, several different merc units field Elementals- heck the Raging Horde (cluster) was made up completely of Elementals before they had to restaff after casualties in '66?
I think the table has Elementals & Salamanders as 11s & 12s on the roll . . . maybe Gnomes too but its been a while since I looked. Rabids did not come on the scene until supposedly '67 but like all the BA made official in the '67 TRO, my headcanon has them with limited availability before that year. For instance I think the Trinity should have gotten combat testing in the end of the St Ives conflict- maybe Yin Long w/o Mimetic armor as a prototype.