I've read that water dogs, the tiger salamander pups, are generally more voracious and cannibalistic than axolotl. If you housed them together, you'd get one very beat up axolotl and a soon to be salamander that would need an entirely new set up once they morph, so they wouldn't be able to be housed together anyway in the long run.
Maybe if the tank was huge, like a 75gal, and you had all of the hides for them to space out, but you'd still end up removing the one later on; it wouldn't be a permanent housing situation.
Were you just curious over all, or are you looking for something a little different to house with an axie?