It seems possible to create a model in Collada 3D Digital Asset file from a JT Open CAD source. You can do that either with some modeling software with support for both of these formats, or through some kind of dedicated 3D/CAD translation software like the Babel3D.
Convert JT Open CAD 3D model format to Collada 3D digital asset exchange data.
We found 4 software records in the database related to .jt to .dae file format conversion.
Microsoft Windows software - convert jt to dae on Windows
A 3D CAD translation softwate
Convert from jt file format
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned jt to dae. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
A 3D product data optimalization software
On-line services software - convert jt to dae on web
A commercial online CAD converter
An online CAD conversion service