Having exactly the same problem. It took a long time, and a lot of trail/error/forum reading to get to where you did (editing info.plist). I removed my 'useless' superdrive also.
Refit has a utility to rebuld partition info as Mac likes it (after using gparted, in my case to grow the bootcamp partition as I made it too small), but after that nothing wants to boot into my windows boot usb key to run the final step which is the repair of the windows install/boot config.
Maybe osx adds some boot info immediately after you commence creating the bootcamp environment with Boot Camp Assistant. I remember it always booted into windows until you finish setting windows up... either by 'Option' selecting OSX on boot, then rebooting from system prefs, boot disk page. Or rebooting from Windows bootcamp tools. This worked also into windows setup if your USB was in. Once you have done that though, nothing wants to boot off your Windows install USB. Not even refit.
Unfortunately for me, that's where the windows repair utility lives which will complete the fix of my partition resize.
Obviously recreating the bootcamp partition would do it. But that defeats the purpose of trying to grow it without reinstalling windows in the first place.
Bloody hell, I already had to open my MBP up as the windows installer likes to fail if you have a HD attached to your Super Drive Sata port.
Might have to wipe, disconnect OSX and reinstall windows all over. Paragon Boot Tune is supposed to be able to resize Boot camp, but the damn thing requires a superdrive to burn a boot disc to!
Only other thing I can think of is that refit ruined something. But I don't think so. FYI I also removed refit and can select the Win Boot Camp partition or Boot USB Key but they fail that way also.
Anyone reading this... make sure your Bootcamp partition/drive is at least 30gb. Windows takes 15-25 (if you include room to move for temp files, caches and updates etc. Then you got apps on top of that.
I think the problem is the way the computer is locked, if your computer has a Super Drive, your Mac is automatically configured/locked to boot from that drive and ignore the USB.
Their is no amount of reconfiguration or software tricks that would change that, what you can do is take out the Super Drive, or try cleaning it with a CD cleaner - the one with the brush.
Best Answer
You need to format the USB drive to use the GUID partition type -- use the Disk Utility on your Mac.
source Apple support docs