At the moment, I would guess that MCP is actually standing up in this scenario, but its not actually redirecting the traffic because its going directly to the proxy (over 9090).
To do what you're asking it would require that MCP toggle the browser settings in someway (to disable automatic detection -- WPAD).
In the end is the result the same? MCP is scooping up traffic that isnt handled by 252, and traffic that understands 252.
Let me know if I'm misunderstanding.