At this time, we only recognize RSA certs. I cannot say when we will support the ECC technology, however, when or if that happens, we will certainly advise you and the community via some public announcement. We usually do this through a blog post. Hopefully you are following us there also.
Please let us know if you have any further questions about TLS, or any other issue with respect to our service, we are always happy to help and advise.
TLS Implementation Lead, Fastly Customer Support