rMBP Mid-2014 Thunderbolt bus bandwidth

I'm thinking of getting an eGPU setup via Thunderbolt going, which will max out the bandwidth available (20Gbit/s) on the Thunderbolt 2 interface.

I'm interested to know if the Thunderbolt 2 controller will be able to handle both ports being maxed out (i.e. 40Gbit/s in total). Is anyone able to shed some light on this?