Get-MailboxLocationPermission.ps1

[CmdletBinding (SupportsShouldProcess = $false)]
param (
    $Mailboxes = @(),
    [switch]$FormatTable = $true
)

begin {
    $MailboxesLocationsPermissions = @()
    $LocationsPermissions = @()
}

process {
    foreach ($Mailbox in $Mailboxes) {
    # Forward slashes are the path delimiter in the Get-MailboxFolderStatistics FolderPath property, but Get-MailboxFolderPermission uses backslashes for path delimiters.
    # Forward slashes in any part of the path resolve to "" in the FolderPath property, so translate it back.
    # "Top of Information Store" in the FolderPath property is simply "\" to Get-MailboxFolderPermission.
    $Locations = $(Get-MailboxFolderStatistics -Identity $Mailbox).FolderPath.Replace("/","\").Replace("","/").Replace("Top of Information Store","")
        foreach ($Location in $Locations) {
            # Exclude permissions checks on the Dumpster non-IPM locations - they won't even resolve to their actual paths this way anyhow, and don't really support special ACLs.
            if ($Location -ne "\Recoverable Items" -and $Location -ne "\Deletions" -and $Location -ne "\Purges" -and $Location -ne "\Versions") {
                try {
                    $LocationsPermissions += Get-MailboxFolderPermission "$Mailbox`:$Location" -ErrorAction Stop
                } catch {
                    if ($_.Exception.Message -like "*couldn't be found*") {
                        Write-Debug "Location `"$Mailbox`:$Location`" not found."
                    } elseif ($_.Exception.Message -like "*cannot call a method on a null-valued expression*") {
                        Write-Error "The value provided for Location was null or improperly formatted."
                    } else {
                        Write-Error $_
                    }
                }
            }
        }
        $MailboxesLocationsPermissions += $LocationsPermissions
    }
}

end {
    # The default output is nigh useless for quickly reading through, so include an option to pretty-format the data, though this does change the types...
    if ($FormatTable) {
        $MailboxesLocationsPermissions | Format-Table -Property User, AccessRights, IsValid -GroupBy FolderName -AutoSize
    } else {
        return $MailboxesLocationsPermissions
    }
}

No Get-Help text yet, but it's fairly self-explanatory. Feed it one or more mailboxes, optionally specifying -FormatTable:$false to retain the native data types.