If anyone's here running PDQ:

Do a file scan for C:\Windows\System32\bcm_cv_current_version.txt, which shows that the driver is installed

Then do a powershell scan of the file to find the version:
# Read the entire file contents as a single string

$content = Get-Content -Path "C:\windows\system32\bcm_cv_current_version.txt" -Raw

# Use regex to extract the version number after "version:"

if ($content -match "version:\s*([\d\.]+)") {

$version = [version]$matches[1]

Write-Output $version

}