The short answer is: Yes, SteamVR is compatible with Aximmetry.

OpenVR is a https://en.wikipedia.org/wiki/Software_development_kit (SDK) and https://en.wikipedia.org/wiki/Application_programming_interface (API) developed by Valve for supporting the SteamVR and other VR devices. The SteamVR platform uses it as the default application programming interface (API) and runtime. Think of it as a bridge between the hardware (VR headset in this case) and the software,  and it is implemented by SteamVR.

Aximmetry supports OpenVR, this means that it can make use of the tracking abilities of all VR headsets that are SteamVR compatible.