I didn't try to connect an external BD Rom to my PS3 but I bet it won't work at all. Technically, there are two different command sets to access flash/hard Drives and optical drives so an external BD Rom can't be accessed as a typical storage device. I doubt SCE put USB optical device driver in the PS3 firmware.Sponsored Links
Besides PS3 is region-locked device despite of its ability to play PS3 games from other regions since PS1/PS2/DVD/BD region restrictions are still here and it would be it would be unbelievable to imagine a PS3 allowing to change BD drive region five times like PC software does.
I'm 100% sure it will not work. There is no support, because there would be no valid reason to have 2 BR drives at once, according to Sony
A very long time ago i hooked up a cd then dvd ide drives through usb enclosure... and of course nothing happened as expected.
maybe if you flash your bd usb to multistandard (if a multi firmware exist) but i dont know if the console can check region.