I've done this. My employer likes me to stay legal, so I looked up the FCC rules about unlicensed operation (I'm in the US), did the calculations, and determined that I could in fact keep the leakage below limits, and the input power to the HS and BTS receivers within proper range. I'm using the BTS at minimum power of course. I use a Minicircuits ZAPD-20-S+ power splitter, which has 30db isolation between the two ports, and a single 30db attenuator on the HS side. With my equipment I need a minimum of 24db attenuation between each transmitter and the opposite receiver. I did not check the leakage as I don't have a calibrated field strength meter but according to specs it should be ok. I've got the numbers if you're interested.