Is it possible to establish openvpn connection to MT OpenVPN server based only on certificates not user/password verification?
I know it is possible with linux OpenVPN implementation.

Now I'm using certificates on server and client side ("Require Client Certificate" on server) but I also must have user defined in PPP secrets and I need to use auth-user-pass option on client side.

Is it possible to establish openvpn connection to MT OpenVPN server based only on certificates not user/password verification?

No.