If I were to buy this game could I access the CAC or is this down now that the servers are down?

You can't buy it. The original game is no longer for sale. The upcoming re-release, titled APB: Reloaded, will be free to download. I'm assuming CAC means create a character, so yes, you can access it and make up to eight characters. However, players that do not pay a subscription fee will have more restrictions when customizing apparel, designs, tattoos, etc. Also, many items must be unlocked by playing in the action districts (the shooting gameplay) before you may purchase them and customize in the social district. APB: Reloaded is in closed Beta right now so you won't be able to try it for yourself until it goes to open Beta.