Please have a look at jira issue https://jira.talendforge.org/browse/TDI-892
You can try to use the / (without double it) instead of \ because the JVM translate it automatically into the appropriated char. This way you avoid the hassle with the \ as escape char.
as file script is generated by Talend, I don't think so (there is a workaround).
Ask as a feature to bugtracker that Talend generate such a file that avoid that 'UNC constraint'.
unfortunatly I'm not able to give you more information.
ps: write a little script that modify syntax ....