You can call vray.exe -version and capture the output. Our Vray is deploy on server but you can find the vray.exe on each machine if you install it locally.
C:\Users\joey>U:\plugins\vray\v35203_maya2017\maya_vray\bin\vray.exe -version
===============================================
V-Ray Standalone, version 3.52.03 for x64
Copyright (C) 2000-2017 Chaos Group Ltd. All rights reserved.
Use -credits option for additional third-party copyright notices.
Build b05f4567 from Jun 14 2017, 22:05:33
Compiled with Intel C++ compiler, version 15
Operating system is Microsoft(tm) Windows(tm), version 6.2,
V-Ray core version is 3.52.03
===============================================
Hey Edwin, thanks for these links. I must have picked up a really old version of that SoftwareAudit script as this one looks different. I will test this out tomorrow when im back in the office.