HD lists both the XM and CB as a "no fit" on the FLTRXSE, as well as for the SESG2/3 models. In the latter case, this is primarily due to the wiring harness inside the fairing lacking the 6B connector found on other models that is used by the non-Ultra Overlay Harness, 70169-06A, for both accessory modules. The supplying of the 6B connector on the SESG2/3 models is well-documented on this forum--suggested search terms: "6B connector." The "no fit" for the FLTRXSE is probably due to the absence of the 6B connector and the solution offered for the SESG2/3 is probably equally effective on the FLTRXSE.
I suggest in the absence of a definitive answer here, your buddy buy/borrow the 2012 Touring Model HD service manual and the FLTRXSE supplement. With those, he can confirm what he will need to supply that HD omitted on his bike.
Also, as an alternative to replacing the console for a "standard" add-on CB installation, he should consider HD's alternative kit that doesn't require the replacement of the console; HD p/n 77108-09A. Due to the underlying "no fit" for CB, he'll also find that HD lists this kit as a "no fit" for the FLTRXSE.
Bottom line: Your buddy needs to confirm if the bike has the 6B connector; preferably from HD's wiring diagram for the bike; as well as confirming the same/difference of the wiring on the 27B connector to the radio--the wiring diagrams for the non-CVO FLTR in the Touring model SM will allow him to i.d. and difference with the 27B connector on his bike.
Carl