SharePoint Server 2010 April 2012 CU was released on April 24, 2012. Previously, you can request to MS Support to download the package.
In the latest announcement on the package KB sites, they are no longer available for download due a technical problem. I am not sure what kind of technical problem on the previous package. I wish a refresh package will be available soon, since I am already download and apply April 2012 CU to my development VM.