Two problems

1. Allowing transfer passengers from US/EEA to skip security, but these will most likely have to pass a passport check as they may exit via the CTA/Domestic or leave the terminal by other means

2. Allowing CTA passengers to reach baggage without a passport check without resorting to UK style messing with buses. This adds some fun as transfer passengers from the CTA won't go via the transfer desk, so EI would need a service desk in the T2 departures area