I have created a ModelBuilder in ArcGIS 10.3 and exported the Python file.
Now I want to use that Python file in QGIS plugin. Can that be done?
Your question distils to whether you can call ArcPy code from within your QGIS Plug-in and whether the machine you are running it on is licensed for ArcGIS Desktop.
If both are true then I cannot see why not, but I suspect that it may be simpler to look for PyQGIS equivalents to the ArcPy tools in Q&As here like QGIS Plugins & Tools that replicate Select ArcPy Tools