Yes, Schluter®-DITRA or DITRA-XL can be installed over vinyl. Some limitations include the following:
1. Cushioned vinyl is unacceptable
2. Perimeter bonded vinyl tile is unacceptable
3. Multiple layers of vinyl is unacceptable
See detail D-V-T in the Schluter®-DITRA Installation Handbook for complete list of limitations, requirements and installation guidelines before proceeding.