In general, yes. But if this is a feeder with a 2 hour fire rating that runs through a building I'm not aware of way to make a J box both accessible and 2 hour rated. If the feeder is truly outside the building I can't see an issue.
The bigger problem is whether you need a 2 hour rating. Most of the old lead cable has been delisted by UL. MI cable no longer meets the two hour rating required.
Messing with this stuff pretty much means you need to upgrade the cable with insulation. 3m makes stuff to bring it up to snuff.
