Indeed, though, it would be awesome to witness the collision and resulting gwaves personally, if such a thing was possible :)
But they're probably only visible from close range (like the 1AU mentioned above) and are too faint to be seen from 1Bi light years like the event that they captured
All of the LIGO observations have been of more basic stellar mass black holes merging together.
Stellar binaries are extremely common, and there is a reasonably large supply of binarys where one star has become a compact object. Their companion stars often drop lots of matter onto them, resulting in a reasonable supply of black holes. Diskoseismologists and others working on Swift have catalogued hundreds of stellar mass black hole accretion disks.
Examples from Swift:
http://adsabs.harvard.edu/abs/2013ApJ...769...16R https://arxiv.org/abs/1112.2249 (preprint version)
Swift also spotted ASASSN-14li which was a star being shredded by an SMBH and forming an early accretion structure. The event has been followed up by other observatories (notably Chandra and the European very long baseline interferometry network). ASASSN-14li is an easy google search term (the trick is knowing the term in the first place :-) ), hopefully you will enjoy some of the hits. :-)
Now that I think about it - yes, of course. It's why they are called _black_ holes. ;-) facepalm
I am not sure, though, if regular (stellar-mass) black holes with an accretion disk emit enough EM radiation to be visible at such distances, or if it would become lost among the radiation emitted by the rest of the galaxy.
(A merger between two supermassive black holes with active accretion disks must be a spectacular sight even from a safe distance.)
