You can indeed combine single phase inverters onto three phase services, but you probably won't want to if a three phase inverter is an option, especially if you are generally not that savvy about three phase systems. Line currents, for example, are straight off the data sheet for three phase inverters but for combined single phase inverters on three phase it involves some calculation.
To add onto factors in favor of using 3-phase inverters instead of compounding 1-phase inverters:
Some utilities either don't allow "stacking" single phase inverters to make three phase, or require your system to balance the total amps on each phase. If you use a three phase inverter, you don't even need to think about this being an issue.
When inverters used to be built with internal transformers, you had more options for setting up single phase inverters on a 3-phase grid. You could adjust taps on the internal transformer, and set the same unit for 208V, 240V, and 277V. The same inverter could connect to 240V split-phase, 120/208V 3-phase by connecting inverters across phases, or 277/480V 3-phase by connecting to individual phases. Current and breaker requirements would change upon configuration to compensate, but the same inverter model would have the same power rating regardless of grid voltage.
Now with transformerless inverters being the industry norm, this is no longer the case. Grid voltage is a firmware setting instead of a hardware setting, and maximum output current is what remains constant. Single phase units are built with 240V grids in mind. Some (not even all within the same product family) can configure for 208V grids, but few (if any) can be configured for 277V. Expect the inverter's maximum output power at 208V to be 13% less than nameplate, rather than expecting 15% more inverter output current to compensate.
