I was having a flickering problem also with my Macbook Pro retina 13 inch (late 2012). It would usually only happen (intermittently) when I picked it up to move it to a different location. In the last month or so, it started flickering occasionally even when not being picked up...and it would only be 1-2 flickers, every now and then.
I have also read in other blogs/posts that the WiFi antennas in the display bezel interfere with the LCD controller causing the display to flicker...and the proposed solution was to replace the moherboard.
I pressed the "option" key on my keyboard and clicked on the WiFi icon on the task bar and noticed that my router was set to broadcast on channel 2 on the 2.4 GHz band. I changed the channel to 1, 6 and 11 and still had flickering when picking up my laptop. This is the bad news.
The good news is that I have a dual-band router (Netgear WNDR3700) and decided I would try the 5 GHz band on channel 153 -- the flickering is GONE ! This seems to have corrected the problem !
It has taken me 2-3 months of searching the web to find your solution. I never thought it would be so simple !
Thank you so much Csupinski !