Im not trying to be a jerk... You can see me on here trying to help people with questions all the time. I know two best buy installers, and the one I know who is the more experienced of the two has an excellent knowledge basis and 15 years of experience in both big box stores and at mom and pop shops. I have seen both his regular every day work and his custom work from previous shops and it is top notch. Since I've talked to him at length we've naturally compared the places we work. So by saying installers at best buy dont know what they're doing is a totally shitty generalization. Some people move to BB or CC from mom and pop shops simply for the stability and good benefits/discounts.
If you dont know how it is in New York(atleast in upstate new york).. let me tell you. Most small shops barely get by, and rely on starter season. Some shops, owners and all.. live from customer to customer. There are some larger shops that do okay, but the customer base around here isn't the largest. By the way most of the shops doing just okay arent pure audio shops, they also do rims and stuff like that. This is the reason some people prefer to migrate to a large company that can always afford to pay you.
That being said, this is what I understand of BB policy as per my comrade in arms there:
If the installer doesnt want to use your wire because it is cheap or damaged or was installed (edit)incorrectly, he doesnt have to. If he does agree it is ok and uses it, they still warranty the labor, and even if its a wiring problem, they will look at/fix it on warranty. You do not have to buy all BB stuff to get a warranty on your labor. That being said, the install bay will not warranty your equipment.. and why should they? If you did purchase the equipment from BB you could either send in for the manufacturers warranty, or you could buy the replacement/service plan.
If you bring in your own equipment, the installers there are supposed to bench test it. If it fasils the bench test, you must pay a fee. If it passes, they install it and warranty the labor. They never warranty an amp or sub... that is up to the company who manufactured it.