Short answer, no it won't. The longer answer on 'what would it take to make it work', would depend on exactly what models of everything you have. "XT" is not specific enough. Read the number off the backside of the parallelogram. For example if you have an M751-SGS, then the best thing would probably be to buy a new set of 9-speed shimano bar ends (or just the right one, if you can find it). Depending on the exact combo of things you have, there may be a JTEK travel adjuster or similar setup that could make it work. JTEK Shiftmate has a huge compatibility chart for your specific stuff.
Bill Lindsay
El Cerrito, CA