Uhhh as some sort of noob apparently I can't include links. I'll attempt to obfuscate.

From here
http://www.bikeradar.com/news/saris-...ch-2009-range/
there is an image linked
images.immediate.co.uk/production/volatile/sites/21/2019/03/Saris_PowerTap_guts-9b7bffb.jpg
which shows a bunch of unassembled wireless Powertaps. The radio module on the "outside", under the screw cap, is distinct from the sensor module PCB glued to the interior of the torque tube assembly.

In the photos there appears to be a black cable running up to the radio, presumably from the PCB, though it is hard to tell. Based on how the battery module is implemented with a bulkhead connector, you would think the radio might have a similarly located connector.

One of my units in question is model 2.4 wireless (ANT). The other is model SL+ (ANT+). Each has its wireless implemented as a module screwed to the hub body, under the cap. I guess that the radio transacts with the sensor board using I2C. And I guess that the sensor PCB is likely generic and agnostic to what wireless module is connected to it.