Vista - Translate WMIC query to Powershell

I've been using wmic for several years and I'm trying adapt some queries to
Powershell.

I'm having a little trouble with this one which enumerates AD or local
membership:

Here's the wmic query for local and AD respectively
wmic path Win32_GroupUser WHERE
(GroupComponent="Win32_Group.Domain='MYDOMAIN',Name='MYADGROUP'") get
PartComponent

wmic /NODE:LocaServer path Win32_groupuser WHERE (GroupComponent =
"Win32_Group.Domain='LocalServer',Name='MYLOCALGROUP'") get PartComponent

Here's my attempt at a Powershell equivalent

$computer = "LocalServer"
$groupname = "Administrators"
$domain = "LocalServer"
Get-WMIObject -computername $computer Win32_GroupUser | where
{$_.GroupComponent -eq
"\\$computer\root\cimv2:Win32_Group.Domain=""$domain"",Name=""$groupname"""}

For AD change parameters
$domain = "MyDomain"
$groupname = "MyADGroup"

The Powershell equivalent works fine for local groups but doesn't return
data for AD group query. I know I can use DirectoryServices for AD queries,
but I'd rather stick with using WMI for both local and AD group queries.

Also is there a way to call wmic directly from Powershell like I can in the
in bat files?