Considering that both the .jt and .model files are CAD formats, it is very much possible that both can be converted between each other using some good CAD software with a lot of file format support, like CATIA or SolidEdge. Some viable choices for jt to model conversion are listed here.
Open JT file Open MODEL fileA CAD converter with huge format support
A CAD visualizaton, analyzation and translating system
A dedicated CAD converter