Basically the signal is pre polarized Horizontally or vertically at the transponder. So the power converter in the STB switching over to 13-19 volts according to the polarity. Vertically polarized channels are working on 12 -13 volts and horizontal channels required 18-19 volts.
The LNB is looking for a steady 13 volt or 18 volt supply and a steady 22kHz tone. One receiver (STB) will always "win" means the receiver supplying 18 volts will win over the other. So in practically (
BUT Impractical ) you can watch simultaneously both H polarized channels or V polarized channels.