No. If you have any influence on it, do not use NTLM, it is an unsafe and deprecated protocol. Security should be dealed with at Webservice protocol level, not at HTTP level.
But probably you are the consuming service and have no influence on this. In that case you have to setup the NTLM - HTTP connection first (the Kerberos / WinSSO module supports NTLM, so maybe you can borrow some code from there). Once the connection is setup, you could stream the webservice request / response over the connection (Newer Mendix versions (3.2 +?) have Core API's for this if I remember correctly).