There was an error in the upstart script for yate.. When compiled from source, the yate binary will be in usr/local/bin and NOT in usr/bin.
The documentation link i pointed to talks about changing the /usr/bin to usr/local/bin in the init script but not in the upstart job script for yate.. When i looked at the script you sent, it stuck me immediately about the location of the yate binary for compiled version (the last line with exec in it)....
perhaps the document needs to mention about it as well.
(and by the way, there was an error was logged in the /var/log/upstart/yate file that /usr/bin/yate was not found)...
makes sense now and i can now start the job and get a pid for it as well!