Users with read access to a site using out of the box web services

Is it possible to use the out of the box SharePoint 2007 web services to get a list of Active Directory accounts and groups with read access to a site? I will need to iterated the SharePoint groups to get all the AD groups.

I know how to do it using the object model but I need to do it for a farm the code is not running in. I am looking at doing a custom web service to provide the information but I want to make sure I cannot use the out of the box web services to do this before I write a custom web service.

Thanks,

Mike