I was summoned!
Are the laptops configured with proxy settings or proxy pac? If proxy settings, then this will likely not work well. If proxy pac, then the browser will fail open if the proxy pac URL is not reachable. If MCP is used with a proxy pac, it works quite nice because MCP will stand up and redirect the traffic in case of "fail-open".
One such instance is my pal phlrnnr, he mentioned it here: Re: MWG Proxy vs. Transparent Bridging vs. Transparent Routing
However I think he has MCP to stand down regardless of when it's in the network.
I hope this helps!