Try something like this
$tagCatName='Backup Job'
$tagCat=Get-TagCategory-Name$tagCatName
Get-VM|where {(Get-TagAssignment-Entity$_-Category$tagCat).Count -gt1} |
SelectName,
@{N="Tags";E={[string]::Join(',',(Get-TagAssignment-Entity$_-Category$tagCat|%{$_.Tag.Name}))}}