MU = Multiple-Unit which for the matter at hand is synonymous with lash-up. In other words 2 (or more) engines running in tandem to provide more pulling power.
If your DCS Remote Commander (DCSRC) can individually control your PS3 and PS2 engines, then those engines can be mechanically coupled and run as a pair. As you know, the PS3 and PS2 engines must be set to the so-called factory-default address which is the only address that the DCSRC can control. But if you can control your two engines one at a time with the DCSRC, then you should be good to go.
As an experiment you might want to run the two engines together but separated (uncoupled) and watch them speed up, down and stop with the DCSRC. It is obviously critical that the two engine behave identically (or near identically).
There are some niceties when using a full-blown DCS-TIU configuration for MU/lash-up operation. In your case, both engines will do exactly the same thing wrt lights, sounds, motion. In prototypical operation, perhaps JUST the lead engine in a MU blasts its horn. Or maybe JUST the lead engine needs to operate its headlight. To each his own as to whether these operational details are ho-hum or show-stoppers. 
