/usr/lib/thunderbird-addons/extensions/{e2fda1a4-762b-4020-b5ad-a41df1933103}/components/calICSCalendar.manifest is in xul-ext-lightning 1:24.4.0+build1-0ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 | component {f8438bff-a3c9-4ed5-b23f-2663b5469abf} calICSCalendar.js
contract @mozilla.org/calendar/calendar;1?type=ics {f8438bff-a3c9-4ed5-b23f-2663b5469abf}
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