Yes it can. You have to tell VEGAS to run the script on startup. Use something like:
"c:\Program Files\VEGAS\VEGAS Pro 19.0\vegas190.exe" -SCRIPT:"d:\MyScript.cs"
This is assuming your VEGAS is version 19 installed in the default location and the script is called "MyScript.cs" and stored on drive "d". Just modify the above for your version of VEGAS and your script location/name.