Stations are fully rendered in normal space (assuming they are within visual distance). As soon as you jump to SC however the station "disappears". Most players don't notice this because they are usually pointing away from the station when entering SC and don't usually see the station "disappear" upon entry into SC. I just got some screenshots to show what I'm referring to, if you try it yourself it is quite apparent and obvious.
First, this is Bluford orbital in normal space:
http://i.imgur.com/tNCPo4C.jpg
This is Blueford orbital once the FSD countdown timer starts, with the station still present as I'm still in normal space:
http://i.imgur.com/TqPHLIm.jpg
This is Bluford orbital as I'm making the transition to SC, it hasn't disappeared yet because I haven't "jumped" to SC yet and the game still has a station to render in that frame:
http://i.imgur.com/GSFDEhn.jpg
This is Bluford orbital the moment I enter SC, it has disappeared completely and I actually fly right "through" where the physical station should be. It simply does not physically exist in SC and cannot interact with me in any way. Assuming I don't actually hit the station itself I should at least instantly become masslocked and drop out of SC immediately upon entering SC. This doesn't happen however because there is no station to render and there is nothing to masslock me. The station simply does not exist as a physical 3D model in SC at all despite being directly in my path (less than 5 km distance) upon entering SC:
http://i.imgur.com/T2QfSr7.jpg
Try it yourself, with any station, you'll see that the stations do not exist as rendered objects in SC as soon as your FSD completes the transition to SC. They are just nav points on your HUD, that is all. The stations can only "masslock" you prior to entering SC but once you've entered SC the station only exists as a "point" on your HUD.