I've had a few searches on the web for this and haven't found anything related.
Using a Buzzard I flew over to the N.O.O.S.E. building and started poking around as it isn't somewhere I have explored yet. (Took me about 10 minutes of fannying around the fences and such to determine that I wouldn't get shot to pieces on a 4-star).
When facing a certain double door whilst inside the buzzard I noticed that the door was fading in and out of transparency. At the right distance from the doors it was completely transparent and I could see that behind it is an interior. On the left side of the doors inside there are boxes stacked upon blue pallets.
This also works if you are sitting inside any vehicle, but as soon as you get out, the doors 'return' and you cannot see through, even if you use a scope at a distance. You must be inside the vehicle to see through them.
I've tried shooting rockets at them, gunning them down, sticky bombs and just shouting at the screen but nothing works to let me in. I have also tried building up a hefty wanted level to see if the NOOSE would exit through this door or something, but no such luck.
The reason I am posting this is because I haven't seen it mentioned before and I am sure there must be a reason why there are boxes inside - it's not just a plain interior, it appears to have been modelled fully from what I can see.
Unfortunately I am playing on a PS3 so I am not aware of how to take screenshots to prove this.
To get to the doors on foot simply enter the front gate using the right hand lane to enter the car park in front of you rather than to go left to the main car park in front of the complex. Go to the far end of the car park and on your left will be a set of pushable fences - push past those and look to your left. There will be a set of black double doors with a single portrait window in each door. The doors are facing the fence gates at an angle if that helps.
This could well be nothing but I want to confirm if anyone else has this glitch or has found any additional information on it.
I did this today on the latest patch on the PS3.