It is completely untrue. I recently flew LHR - HEL and found that they closed the CE boarding lane at T3 just before I was about to use it. The staff member continued to board the ET passengers as I waited - finally he decided to call me forward. Waited in the holding pen a few minutes to be put onto buses to the aircraft.
The whole experience (apart from the rude agent) was repeated in the opposite direction. I suppose even worse as there was no fast track security for CE passengers at HEL airport!
I've heard stories about additional buses being used for CE passengers, but I've never experienced this... Why advertise something you don't provide?