Yes, if you have the CCA add-on with Liberty Mutual you're guaranteed OEM BMW parts; at least that's my understanding and what I've heard from others. Apparently some other insurance carriers that default to aftermarket parts offer (but don't advertise) an "OEM parts only" addendum you can request for your policy (likely at additional cost) that will mean they'll pay for OEM replacements. You can always call your agent to ask a) whether they default to aftermarket parts, and b) if so, whether they have an OEM-only option.
Also note that in some states, the law states that insurance companies CANNOT prevent you from demanding OEM replacements on your car -- but the law does NOT say that insurance companies have to PAY from OEM parts, so in those cases if you want OEM, unless your carrier offers OEM replacements by default, you'd have to pay the difference from aftermarket out of pocket. There are some exceptions to that though, even with aftermarket replacement carriers. For example, your car needs to be restored to "pre-accident condition", so if an aftermarket part clearly doesn't fit or function correctly, the carrier will pay for an OEM part. I just heard about this at a presentation from a body shop this past weekend where the owner said he'd seen constant occasions of insurance carriers starting off wanting aftermarket even though the owner knew the aftermarket part wouldn't work correctly, but he ordered it because he had to, demonstrated to the adjuster that it sucked, and then had to go order OEM anyway. Of course the loser there is the customer, whose car was out of commission longer.
FWIW, I use Amica Mutual. I called them about the OEM replacement question and they told me that while the replacement parts may not be NEW, they will definitely be OEM. I honestly can't say enough good things about them in general, even though I've already written about them in other threads here. I just added renter's insurance through them, and every time I talk to them on the phone I'm left thinking they were an absolute PLEASURE to deal with -- how often can you say that about your insurance company? When I had a claim on a previous car, the other party was at-fault but turned out to be shady and unreachable, so it looked like I was going to lose my $1000 deductible. Well Amica called me 7 MONTHS later (LONG after I'd considered that money gone) and said they'd finally tracked her down, gotten her insurance company to accept liability, and I would be getting my deductible back -- I was especially impressed because my deductible was greater than the amount they'd had to pay to fix my car. That's how you build customer loyalty.
I'd never heard of them before but when I was shopping around they were rated top in customer service for something like 12 years running by JD Power (behind USAA and one other company not open to the public), so I called them and it turns out they also gave me the lowest price. I was initially worried they were just giving me a great deal now and wouldn't be there for me when I needed them, but obviously that hasn't been the case at all. Plus unlike USAA and many other insurance carriers, they haven't yet switched to the "No coverage for driving on racetracks for any reason" wording, so HPDEs are still covered with them.