Metro-E would normally be treated as a private network in that you can use exclusively private addressing and there is no exposure to the Internet. However it still does ride across your carrier's shared infrastructure and by itself provides no confidentiality protection from the carrier themselves. Overlaying DMVPN (or any other cryptographic protection) adds that confidentiality.
I would not normally expect it either unless the customer had some regulatory or compinace requirements that dictated enceyption for their data.
