"Is use of 'lucubrate' indicative of something being written by an ordinary working person for an audience of ordinary working people?"
Nobody is claiming that all of these songs came from ordinary people by any means, but this type of poetic verse is to be found in many Dublin street songs
One of the best of these songs, 'Mullingar', was written by a Civil Engineer designing bridges.
Irish language traditional song from 'The Peasantry' has strong roots in Bardic Poetry
It's often forgotten that premier performances of Shakespeare's plays were for the delectation of 'the sweepings of the London streets and Londoners were queuing up for the next instalment of 'Great Expectations' and Nicholas Nicholas Nickleby
Similarly, Synge, Yeats and especially O'Casey were writing for the 'ordinary' people of Ireland - they were 'popular' playwrights
There's a sound basis for the story about the navvie being interviwed for a job with McAlpine   
He was asked what the difference wwas between a joist and a girder
He replied. Joist wrote Ulysses and Girder wrote Faust
Jim