Using multiple ports to transfer data to single device
That datasheet does say " It is possible to enable multiple interfaces simultaneously".

So I am going to guess that yes, you can use multiple protocols at once. But most likely, each command is executed using one link only. 

For example, if you want higher transfer speed, then you can not transfer half of the frame over serial and other half over RS422. But you may be able to command "send frame 1" on serial link, and "send frame 2" on RS422 -- effectively doubling the throughput.

(note: this is all guesses. I never used this particular camera model)