Good morning,

yes it is possible.

If you observe PWS panel or Bluemix you can observe that information.

Every organization has binded a OrganizationQuota and this definition affects to every applicattion deployed in any spaces binded to that organization.

The REST methods used to get the definition is:

http://apidocs.cloudfoundry.org/213/organization_quota_definitions/retrieve_a_particular_organization_quota_definition.html

The method to read the memory used is:

http://apidocs.cloudfoundry.org/222/organizations/retrieving_organization_memory_usage.html

You have an example here:
https://github.com/prosociallearnEU/cf-nodejs-dashboard/blob/master/services/HomeService.js#L69-L79

Remember that the memory used is the active memory. You can many applications staged but stopped. When you sum memory to the counter is when you start a new application to set of applications running in a space.

Juan Antonio