Will take a lot of pics describing how it works.
http://mqb.pl/en/tutorial-retrofiting-lane-assist-sign-assist-light-assist-5q0980653/
this is basically the way im going to do it but much cleaner
I'm the author of this solution. To bo honest it was just proof of concept, right now I've done it in OEM-like style, without changing windscreen. I'll write it down and publish on my blog during the weekend.
Feel free to ask any questions if needed. I've completed 5Q0 camera retrofit (total cost around 60$). Right now I'm working on 3Q0 camera retrofit (from MK7.5).