I have no idea whether bmi's current longhaul routes are successful or not, but I am surprised that their focus is entirely on the USA when there are good profits to be made on other destinations from LHR, which bmi could service more easily. I get the impression that the SAA sub-lease has been an operational success - it seems that SAA were highly impressed with the A330 and may order some of their own - but whether it covered bmi's costs is another matter.
As for a 'merger' between bmi and Virgin, I think that's now history. Virgin's branding is far too strong to be risked by dilution with another company (as SQ realised), and getting involved with European-based full-service shorthaul seems to be a good way of losing your shirt. As far as I can tell from what's published here and in the newspapers, bmibaby is keeping the shorthaul balance sheet in the black, and baby would be very unlikely to be included in any deal. Virgin's current codeshares with bmi cover their feeder requirements in the UK; owning the airline wouldn't help their balance sheet or the passenger loads. As I see it, it ain't gonna happen - but RB and Bish could well prove me wrong!