Depending on the circuitry, it's *possible* two different brand components can drive the same emitter. However, it's also possible that something *could* be damaged by direct connection (without diodes), due to differences in internal resistance, ground paths, voltages, etc. You won't know for sure, unless you either try it and see, or examine schematics for each device.

Bottom line -- why take the risk, when diodes are only a few cents?