While I can't recall any songs to be sung to the beasts there is a large Australian contingent of written materials about bullocks in both prose and verse.
The ones that easily spring to mind are:
'I draw for Speckle's Mill, bullocky-o, bullocky-o'
'Twas gettin dark, the team (of bullocks) got bogged, and hungry too was I, and the dog he shat in the tucker-box nine miles from Gundagai'
The classic poem 'Holy Dan'
Bullock teams were much more common than horses in rural Australia before the introduction of motorised vehicles. Oxen were much better suited to the Australian environment and were used extensively for logging and pulled huge loads of wool and wheat to the nearest rail or riverboat location. It was only after WW11 and tractors became affordable for most farmers that bullock and horse teams disappeared other than for eccentrics and those wishing to preserve our history. (Or are they the same thing??)
Other Aussies can provide lots of material if you wish. The best book I can think of is by Australian collector, Ron Edwards. The name escapes me but it's something like 'The Great Big Book of Australian Folk Song. I wouldn't be surpised if there was a more specialised book on this subject.