This permissions issue because the credentials of the user running the service on a Debian distro are not the same as the credentials of the user.
For example, when logged in as the 'niru' userid, the 'id -a' command returns this output:
niru@node2:~$ id -a
uid=2001(niru) gid=2001(niru) groups=2001(niru),4(adm),27(sudo)
In the context of the service process, the same 'id -a' command returns:
uid=2001(niru) gid=2001(niru) groups=2001(niru)
So, in the service context, the niru userid does not have permissions to read the /var/log/syslog file.
This bug in Upstart is documented here: https://bugs.launchpad.net/upstart/+bug/812870
Adding the setgid parameter to the service startup file resolved the issue.