> The other aspect is that these torpedoes can still be wired to the ship so you can continue to use the host sub's arguably better passive sonar systems and let the attacking torpedo get VERY close.

I don't know if there is any public data about how long the guidance wires are, but tens of kilometers seems like a pretty safe bet. Classic wire-guided TOW missiles have 3+ km of wire and are much smaller than a Mk-48 (about 6" diameter, vs 21")