The first thing to say about this song is that it is not traditional. It was written by Dominic Behan. It is on The Dubliners' 1983 Album "Prodigal Sons"
The lyrics that have been posted here seem to have the lines mixed between the verses. They certainly don't match the (original?) Dubliners version anyway.
There is no company called "FitzMurphy". The writer seems to be getting muddled between FitzPatrick and Murphy both are large contracting firms and both figure in the song. Bonus is another similar company which is also mentioned.
If anyone needs the words I will transcribe them from the record and post them here. You can get me at email@example.com
Regards John Hill