This gist is a powershell script utilizing AzureAD Preview to get the claims mapping policies for a service principal.

Get All AAD Policies for SP

Connect-AzureAD
Import-Module "AzureADPreview"
$appID = "...guid-of-the-AppID..." 

$sp = Get-AzureADServicePrincipal -Filter "servicePrincipalNames/any(n: n eq '$appID')"
 
$existingPolicies = Get-AzureADServicePrincipalPolicy -Id $sp.ObjectId `
                    | Where-Object { $_.Type -eq "ClaimsMappingPolicy" } 

$existingPolicies