I have pre ordered the digital upgrades for BF4 and COD Ghosts. I understand thats over 80GB's worth of data for the PS4 for both games - which will put me over my data cap. My question is - do I have the ability to start the install from a physical disc? My buddy has bought the physical discs - I was wondering if I install from his discs - then go to PSN to begin the digital download editions I purchased - will the system recognize most of the data already present and just download what is missing (ala Steam) ?
No. You can't.
The disc based games are CACHE files.... not an actual install.
If your friend doesn't have a data cap, take it to his house to download your games. Or use the local Libraries' internet