However as Stoney indicated, I'm pretty sure the Navy and Marine Mitchells carried them and used them in combat.
As much as I would love to think that the B25's used torpedoes in combat, from the info I have been able to find they didnt. (The Navy B25's were called PBJ-1's by the way)
All of the the PBJ's in WW2 were flown by Marine bomber squadrons... and for those who havent been under a rock for the last 225 years, the Marines ARE part of the Navy... so I guess you "could" say they were Navy PBJ's. Just dont ever tell a Marine that if you are standing within arms reach.
Anyway.... back to the torpedo issue. In order for the PBJ to carry a torpedo, the bomb bay doors had to be left open, and a special frame put in place. The torpedo was actually slung under the plane... externally. While it was tested, and "may" have been carried by PBJ's on patrols... there is no evidence that any were ever dropped in anger during the war.
One of the articles noting this, is from CAF sources, and are from interviews of actual PBJ pilots who flew during the war. You can find it here:
http://rwebs.net/dispatch/output.asp?ArticleID=51Its a great article, and worth the read just for the stories it tells.
The most accurate information that I have found is from the Navy's website. It says that "External carriage of a torpedo under the bomb bay, with the doors open, was also developed and tested during 1944." It doesnt state anywhere it ever made it into combat. Here is the article on that also:
http://www.history.navy.mil/branches/hist-ac/pbj-1h.pdfAgain... a good read just for some "Mitchell" history.
So... the official verdict on the B25 carrying a torpedo in combat is 99% no... although it COULD.