Is there a way to distribute the Beast computations across multiple computers?
I've installed Incredibuild with XGE on several computers. I think everything is configured correctly, but it is not using XGE. Does Unity call ILBStartJob with ILB_RD_AUTODETECT?
As mentioned in my comment above, Autodesk has a Distribeast solution for distributing Beast renders. More info on Beast is available from the Autodesk web site. Beast was developed by Illuminate Labs, who Autodesk acquired about six months ago. Unfortunately information is pretty scarce on the Autodesk web site, and illuminatelabs.com now redirects to Autodesk.
I stumbled on some more info here, which mentions a distribeast.exe. This executable is not bundled with Unity, which seems to confirm my suspicions.
So I think your options are:
License Beast directly from Autodesk with the Distribeast component.
Implement your own job distribution system, launching Unity\Editor\Data\Tools\Beast hebeast.exe directly. (You would need to determine the command line interface and other inputs, not sure what that would take.)
According to this (rather old) gamasutra article, tiered pricing is available for Beast, but that was prior to the Autodesk acquisition. The Autodesk web site doesn't have pricing information, but it does include a request form for a trial version of Beast.
Probably worth contacting Autodesk and Unity to confirm all this and see if there are other possibilities.