Short answer is yes! I own an Onkyo NR-TX 636 Receiver which I have the SoundTouch Wireless Link Adapter connected to through the RCA cable. Plus I own SoundTouch 120, two 10's and 20 as well as the link adapter. They all work great together throughout my home.
You can hook up your CineMate 2.1 through the RCA cable on the back of your headunit. All the cables are include in the box of the adapter including the RCA cable adapter. Below is from Bose Website concerning the SoundTouch Wireless Link Adapter working with older Bose systems.
"The adapter has three common outputs (optical, AUX and RCA), so anything that supports one of them can become a SoundTouch wireless music system. Most stereo systems, home theater systems and docking speakers are compatible—so chances are, what you have in your living room will work after a quick plug-in and setup. Already own a Bose system? Many of them are compatible, too, including most Lifestyle, CineMate, Wave, SoundDock and SoundLink products."
I hope this helps.
PS I own two SoundTouch Wireless Link Adapters, one is in my son's room.