In the IR stuff, there are always two players, the IR Device, containing one or more <ir> declarations, and the IR Transmitter, containing the SendProntoCode action that's responsible for delivering content to the physical Blaster device.
The IR Device gets associated with the IR Transmitter by the metadata field (referenced earlier)
Now whether this is done via codegen, or whether it's just a function of the engine, that's not clear. You used to be able to view the source of a plugin's codegen, but that functionality was broken in MiOS some time ago, so you can't use that trick anymore.
Either way, the [string] contents of the <ir> block, from an IR Device file, is delivered "as is" to the SendProntoCode action of the associated IR Transmitter Device.
In most cases, like the GC100, the Kira and the SQBlaster Plugins this information is, in turn, passed simply on to the physical IR Blaster for interpretation.