*disclaimer*: the following post is made with half-remember rules, assumptions, and not a lot of fact checking :D
re: the ECM version, I don't think people are being sneaky/evil enough when coming up with possible uses for BA with ECM.
1) The BA ECM has a 0 hex radius, and thus not only 'hides' the BA it it carrying, but any other Unit in that hex, yes? Even if that unit weighs 100 tons, is powered by an XL engine and is carrying multiple Ultra AC 20's (or other short range-high pain weapons) >:/!
2) without a Active Probe (or similar equipment), the way to detect a ECM field is to enter it's affect radius, yes? So, against a unit that is concealing itself with a Guardian ECM or Clan ECM you can be up to 6 hexes away and know that "something" is out there, somewhere. Against a Hidden Unit that is in the same hex as BA ECM, you can be 1 hex away and NOT be aware there is an active ECM field and NOT detect that Unit :o
to heck with using the Sloth Interdictor to break up enemy C3/C3i .... I'd be using it to conceal my Units (especially in Urban / double blind games) 8)
hehe - this tactic (using BA ECM to conceal fun/evil units in hidden/double blind games) is a good reason for putting Active Probes on Units :D