We originally discovered the glitch on how to put any vehicle inside a garage, while in the GTA forums someone was able to discover how to insure them.
Here is how to put them inside.
1) find vehicle of preference, be that police cruiser, FIB buffalo, swat van, etc...
2) drive to your garage and put the vehicle close enough to your garage so that it tells you that It cannot be stored
3) when you exit your car you should actually get the animation for entering your garage, this is fine, after this is done head back to your car, but this time play close attention to the following.
4) you have to aim in opposite direction of the garage preferably with an assault riffle, keep aiming and hold triangle to enter your vehicle (aiming with a gun prevents the animation from happening getting you closer and closer to your garage which is what we want). your body should be half way through your car, meaning that you must be aiming opposite of the garage when you are between the back door and front door of your cars, and of course your card should be facing forward towards the direction of the garage.
5) if you did it correctly you should trigger both animations, entering your garage and entering your car at the same time. if you do not get it right the first time keep trying, and also try closer or further back depending on what you get, sometimes you will enter your car and exit it automatically, this means you are closer and closer to getting it inside.
Once this car is inside you can do the same method for the following.
Okay, here's how to insure the vehicles.
Step 1. Get the vehicle you want in the garage.
Step 2. Get any other vehicle that can be insured.
Step 3: Insure that vehicle, and put it in your garage.
Step 4: Take the insured vehicle out of your garage, and blow it up.
Step 5: Go back into your garage, and get in the car you want to insure. DONT DRIVE IT OUT YET
Step 6: Dial Mors Mutual insurance, and keep it at the menu where you can select the car.
Step 7: Drive out of your garage now, but don't close the mors mutual menu.
Step 8 :During the cutscene of you leaving your garage, the menu will pop back up, now confirm it.
Step 9 :Re-Glitch your vehicle back into your garage. (This is important, if you don't do this or sign out during this time, you will lose both cars)
The car should now be insured after you drive it back out.
Sorry for the delay, It took me a while to figure out step 9
This may only work with garages that have drive out cutscenes.
Thanks to Bidwel for the great find, if you need help with any of the two you can add Ross on the XBOX (Rossjtboss), for PSN me (kennyloko89) or Batman (leomunoz7) or Josh (iJoshhyy)."
I post a comment about it on one xenragedcinima's youtube videos asking him if he could look into storing cop cars in our garage, since he's the one who found most of the glitches in GTA Online. Some guy commented back saying it's a mod. He also said he seen a guy with a fighter jet in his garage as well. I wouldn't doubt it either, considering this guy hasn't replied back to any of our comments, so I'm assuming he has mods or he's a dick and doesn't want to share his secret.
Lol. Sorry sorry I just got carried away. You know I've been on here since a year ago so if I knew it of COURSE I would share with you guys. I'm in a crew and the commanding officer figured out a glitch to get these cars. He posted these two pictures and the only way to learn it is by completing two training sessions (apprx two weeks.) SO, as SOON as I learn it I will pass it along as fast as I can.
I think im gonna go after that Sherrif Granger this weekend. Is there any other way to get it other than a four star wanted level?
If not online (or maybe this would work online too, idk I haven't really played online yet)
Buy the best armor @ Ammunation, (I did this as Michael BTW), pick any random car and steal it, upgrade to full armor and bulletproof tires, make sure you have plenty of uzi ammo. Go to the train tracks at Sandy Shores and get your 4 star wanted level. STAY IN YOUR CAR just keep driving around killing all the cops til the SUV shows up, kill all the f*ckers on it (and the driver... but WAIT until he gets out otherwise you'll die when your character takes his sweet ass time dragging his body out). Pull up beside the driver side door (you should still have enough armor to survive switching cars) get out and don't even bother shooting anything, just get in the SUV and haul ass down the train tracks till you reach a long tunnel (heading towards Paleto Bay). Once you get in the middle of the tunnel just stop and wait for the wanted level to go away. You shouldn't have cop trouble following you on the tracks the AI will usually lose control and crash if they try to follow you anyway. That's how I did it and it was pretty easy. I think I did it on my 3rd try. Didn't have to use quick save or cheats.
That is a lot of work, just go to the prison because it's an automatic four stars drive around the parking lot until it shows up and grab it.