I think the Can Bus is the least of your problems. The mk5 sensors shouldn't have the technology required to work with the OPS ECU. You need to upgrade the whole system. I have both my Golfs with OPS front and rear, by the way.
who said so? It's a lie. OEM parctronics works fine with OPS, only "OEM" cobra ones, don't work.
potentially this may be true as its the parking ecu that sends the signal to the can bus for the stereo to display.
so vw may have introduced a parking ecu made by bosch that's compatible with old sensors but ops connects to the powertrain can bus and not the convenience can bus which the mk5 has as standard.
its just sometimes easier to fit the Valeo sets which will work no problem for people without sensors
with regard to original post, 1 your oem wiring is connected to wrong can bus for ops
2 I don't know of a bosch parking ecu that supports ops
3 changing to valeo sensors isn't a 5 min job as your sensor holders being OEM will be plastic glued to the bumper not necessarily stuck with double sided foam like they should be, the bosch holders don't hold the valeo sensors you'll have to change them.
quick cost for the job say 200 with the kit