It would seam unlikely since the signals come from different Satellites and require different tuners. The '03 FM modulator units installed by the dealer may have been able to wire in a Sirius tuner and use the XM antenna and run them through the XM controller, maybe?

I have a Kenwood Sirius controller in my sunglass holder of my 2000 Accord and the antenna is on the rear shelf.

If you really want Sirius you may be able to use parts of the '03 XM retro fit kit and use a Panasonic or Pioneer Sirius controller if they fit in the cubby area and place the sirius tuner in the trunk. You may be able to locate the Sirius antenna just the same way as the '03 cars as well near the rear speaker in the car.

But using the XM tuner to interpret the Sirius codex seams unlikely.