I've seen a few of those rail track anvils, and watched part of the process of one being made. The fellow used a 2x72" belt grinder with decent horse power and pretty high revs. The stuff that doesn't look like an anvil grinds away fairly quickly.

I think if it's for using, it might best be used as a specialty bench block. Even though they have a little heft, they bounce around uselessly if the work is struck with more than a little tap. If they're firmly attached to some base, then they lose convenience and may as well be switched out for a conventional anvil.