As others have said, the Paintball tanks will hold 4500 pounds of pressure but the problem for PCP air rifles is that the Paint Ball tanks are regulated at around 900 pounds. That means you can only pump your PCP up to 900 pounds from a Paint Ball tank.
Pyramyd Air has the same style tank, by Venturi I believe, but it's regulated at about 2800 or 3000 pounds. It's a 90 Cubic Inch bottle, exactly the same bottle that Paint Ball types use, but the regulator is much different. If the Paint Ball crowd used this regulator, it'd rip the paint balls apart in the gun, or kill someone on the field.
Well worth getting one of these for your PCP though. At $300 they aren't cheap, but they do come with everything you need, the valve, fittings, regulator and bottle. Costs $4 or $5 at the paint ball shop to fill.
I have a Marauder and the Venturi tank. It's a great combination for shooting without killing yourself with a hand pump.