Insurance companies can vary in how much they cooperate about seat replacement. If the insurance company balks at replacing the carseat(s), you may need to present the insurance company with FAQ information or other documentation from the carseat manufacturer and/or NHTSA to back you up.
I saw from your other thread your crashed seats are a Graco Snugride and Evenflo Triumph, and both of these manufacturers advise to replace their crashed seats in their FAQs. Here are the FAQ links to give you some backup to pursue replacement with the insurance company:
Graco says to replace the carseat after any type of crash according to the FAQ at:
http://www.gracobaby.com/customerservice/faq_category.aspx?catID=1#132.
Evenflo’s FAQ at
https://plweb.evenflo.com/faq_detail.aspx?faqid=2273 instructs parents to discontinue using the crashed seat immediately.
Here's a link to the NHTSA criteria for replacing crashed seats, which is secondary to the above manufacturer's recommendations, but also will back you up since your crash sounds like it was not just a minor crash (undrivable car equals not minor per NHTSA):
http://www.nhtsa.dot.gov/people/injury/childps/ChildRestraints/ReUse/RestraintReUse.htm
If the insurance company gives you a hard time even when presented with the manufacturer’s guidelines and/or NHTSA criteria for crashed seat replacement, ask the insurance company for a document stating it assumes full liability if the crashed carseats fail to properly protect your kids in another crash. Insurance companies do not like hearing the word "liability," and this approach has worked for other parents when insurance companies weren't cooperating about covering crashed carseats.
Some insurance companies will tell you to just turn in the receipts for new seats and turn over your crashed seats (good idea to cut up the harness and mark the seat with "CRASHED - DO NOT USE" in permanent marker, and save the seat covers as spares if your replacement seats are the exact same models), while others will act like they've never heard of the concept of replacing a crashed seat before and require additional convincing. Some companies will try to give you the depreciated value of your crashed seats, while others will cover the full cost of the new seats. I would personally push for full reimbursement of the new seats because that's what it takes to get your precious children into safe seats again, KWIM?
Hope this helps, and good luck to you.