Do Apple Thunderbolt displays work with Ubuntu 14.04 on 11,2 Macbook Pros with Iris (integrated Intel) graphics?
As of mid-2015, probably not - although I haven't personally tested it. Andreas Noever wrote the initial kernel support for Thunderbolt and his version 3 features are listed here
I have a 11,1 MacBook Pro with Iris Graphics running Ubuntu 15.04 that supports DVI monitors via a DisplayPort (DP) adapter - but this setup only uses the Thunderbolt port as a DP port i.e. there is no PCIe transmission being muxed.