This small script will get all the services that are configured with a RunAs account
The service will be using several possible accounts like LocalSystem , Network Services.. and also a domain account.
The common thing is the service that will be using a domain account should have the UPN (FQDN) or SamAccountName (NetBIOS)
$Netbios=(Get-ADDomain).NetBIOSName #Get the Domain NetBIOS Name
$fqdn=(Get-ADDomain).dnsroot #Get the Domain FQDN Name
#The WMI Query that will be used
$WMIQuery="select * from Win32_Service where startname like '$Netbios%' or startname like '%$fqdn'"
The result should be something like this.
SystemName caption startname
---------- ------- ---------
HQ-SRV-N1 SQL Server Reporting Services Domain\report