Since I could not find any other threads regarding the issue of using all 3 wireless comms systems with the Pixhawk, here is my experience on that topic.
I just created my own splitter cable to connect my bluetooth module with Tx & Rx and OSD with Rx only and plugged it into the telem2 port. Telem1 port still powers the 900mhz radio. Everything works fine so far.
OSD shows all data, so does Bluetooth. When I use either bluetooth or the radio system to change flight mode, the other device sees it and changes display. If I use the transmitter to change flight mode, both Tower (android phone via bluetooth) and MP (windows computer via 900mhz radio) see the change immediately. All other data is shared as well.
Thus, it is possible to get all of the telemetry data simultaneously from all these various devices.
Hope it helps...