Found this site doing a search on bx cable. Just purchased a house that soon after (talking couple weeks after closing) was hit with several violations.
Opening anything is like opening a can of worms with this house, over 100 yrs old. However intentions of doing it were always there but now on a little different time line now that we have court dates. ;-) huge inconvenience when you have the monkey on your back.
That was one of my hardest things to adapt to, when I first moved here 13 years ago. I grew up in Jersey, home of Romex and BX. I bent pipe maybe twice in all my work out there... and hated it. When I bought my first house 7 years ago, the first thing I had to do was rewire the whole thing- old cotton jacket wire, with open splices wrapped in friction tape (they were quite impressive western union splices, but arced like an SOB). I piped everything I could get to, without disturbing the old plaster/lathe.
Now, I have to say... I love conduit! Doesn't hurt that I am pretty good with a bender, either.