Although I have not tried this, you could probably find the ICS Camera icon somewhere in the theme zip, or if not, you could find a png of it anywhere online, and then replace the icon on your home screen using Apex (or practically any launcher). You would, however, still have the HTC themed buttons in the app. I also use this camera with this theme, but I still have the modified HTC Camera icon—maybe I will also try to replace mine with the ICS icon sometime...
UPDATE: I pulled the camera icon from the theme (system/app/HTCCamera.apk/res/drawable-xhdpi) and put it on my home screen. It seems to have worked. I am attaching it, as well as the ICS Camcorder icon, in case anyone else wants to replace the icons but doesn't feel like extracting them from the apk in the zip.