SCOM: Get Overrides from Management Pack

Here's an example of how to retrieve all overrides from a specific management pack and get additional information about the overriden rule and override context.

Get-ManagementPack | Where {$_.DisplayName -match "Your Management Pack"} | Get-Override | % {Get-Rule -Id $_.Rule.Id | Select DisplayName
; Get-MonitoringClass -Id $_.Context.Id; Write-Host $_.Parameter: $_.Value}

To manage all your overrides you could use a tool like OverrideExplorer.