Yes, as long as they were registered before the deadline. By Federal law, the serialized receiver is the firearm. California didn't come and check to see whether there were parts attached.
That said, it wasn't necessarily easy to get those parts, before the Cal Guns Off-List Lower revolution. Some vendors (Cheaper than Dirt, Sportsman's Guide, et al.) still won't send any AR parts to CA. There's no legal reason for them not to, but I guess they don't want to try to decipher CA's laws. If you try to read them, you'll know why.
The same thing happened later, when CA banned .50 BMG rifles. People bought whatever part was serialized, e.g. a single-shot AR lower for under 100 bucks, and registered it as a .50 Cal rifle just in case.