Be alleged in a lawsuit[0] that ms settled without admitting wrongdoing for US ~$23 million that Hitachi, Compaq and others vacated agreements in place to ship pcs preloaded in dualboot configurations with BeOS and Windows due to ms anger and resulting anticompetitive threats.
Be was pretty much a shell company by the time the lawsuit was filed and resolved.
I don't think Microsoft ever addressed BeOS specifically, but pretty much everything they did to ensure no PC manufacturer has any financial incentive to install anything but DOS or Windows on their PCs was as effective against BeOS as it was against OS/2, DR-DOS, DesqView etc...
I'm not entirely sure what you're asking for (obviously I have no new evidence of ancient history), but I'm generally referring to this type of thing: http://www.birdhouse.org/beos/byte/30-bootloader/
I thought that BeOS was interesting, but not compelling enough to make a switch to (much like the NeXT stuff).