Spike it's plastic is manufactured by Color Technologies (who happens to own spike it and lure works) so no it is not Calhoun plastic they sell but rather it's their own.
Calhoun manufacturers their own, MF mixes their own, Lurecraft mixes their own, I have heard DoIt's is Poly One (just what i've heard albeit from a reputable source), Chemionics manufacturers their own as well.
There are quite a few formulas for plastisol, It all comes down to the quality of the resins etc. used in the plastic.