Absolutely. The auto-approval rules of Company B are applied by GROUPNAME.
The auto-install rules are applied by POLICY.
As long as you create the Company A GROUPNAMEs on the Company B WSUS Server,
it is as simple as redirecting the clients to the new server.
Remember this: WSUS knows *nothing* about Active Directory or AD/domain
Group Policy is used merely as a mechanism for loading configuration data
into the registry of the client.
Once the client is configured, the WSUS Server and the client are oblivious
to the presence or absence of Active Directory.
Lawrence Garvin, M.S., MCITP(x2), MCTS(x5), MCP(x7), MCBMSP
Principal/CTO, Onsite Technology Solutions, Houston, Texas
Microsoft MVP - Software Distribution (2005-2009)
MS WSUS Website: http://www.microsoft.com/wsus
My Websites: http://www.onsitechsolutions.com;
My MVP Profile: http://mvp.support.microsoft.com/profile/Lawrence.Garvin