As LGNZ president, he was at the workshop to welcome and assist with the training of around 28 new mayors.
Although he had contemplated missing the workshop, Mr Yule said after seeking advice from the council's legal team, he was told he did not need to attend as yesterday was a technical hearing.
One of the councillors said he was disappointed Mr Yule had not attended.
"It is in effect an inquiry about Hastings, and the water issue," Simon Nixon said.
"I do think that when Lawrence's term in [LGNZ] ends it will be a good time for Hastings, because it will allow Lawrence to focus more on Hastings' needs."
Mr Yule has been criticised previously for his absenteeism from council because of his commitment to LGNZ.
When asked if it was a good look to have missed the first hearing, Mr Yule said he had done everything he could in terms of seeking advice on whether to attend.
"[The legal team's] view was it was not necessary to attend today as it was procedural," he said. "It made no germaine difference to the hearing if I was there."
"The mayoral training for all mayors in New Zealand has been booked for three months, and I couldn't with 10 days' notice unravel that," he said. "If the legal team had said it was important to come back I would have."
"In an ideal world I wish I could have done both," he said, adding he intended to hear as many of the remaining hearings as possible.
Yesterday's hearing was opened by inquiry chair the Honourable Justice Lyn Stevens QC, and concerned procedural matters, including setting out the course of the inquiry over the next five months.
It was not about looking at facts or evidence, Mr Yule said, but about "procedures, and getting the show on the road".
Appearances were called for from interested parties, on preliminary and procedural matters. It was also discussed whether to conduct the inquiry in two stages.
The first would relate to causes and issues of fault, and then the second stage dealing with systemic matters and possible changes needed for the future.
Acknowledging a tight time frame until the inquiry was to report back, Justice Stevens said they hoped to have all hearings completed by Christmas.
In his opening statement, counsel assisting the inquiry Nathan Gedye QC said as well as the outbreak being related to the death of three people - one of which was being investigated by the coroner - and the contracting of secondary infections, the event led to a loss of confidence in Havelock North water, and had given rise to questions around untreated water in New Zealand.
Speaking on the role of participants, Mr Gedye suggested all parties provide information on issues of focus in the inquiry - such as relating to their role, and responsibilities in relation to drinking water.
He also requested information about the contingency plans, and preparations in place for a contamination event.
It was not expected that all participants would have information to contribute on all issues - Mr Gedye agreed with the example of the regional council which would have information relating to the Brookvale Bores, while the Hawke's Bay District Health Board would have facts around the outbreak itself.
In his view, "this inquiry should focus only on what matters, and what should be learned for the future".
The inquiry would look at fault, but not at criminal, civil, or disciplinary liability.
Those who appeared yesterday included Hastings District, and Hawke's Bay Regional Councils, the Hawke's Bay District Health Board, MWH New Zealand, and Crown Law on behalf of the Ministry of Health, Ministry for the Environment, and the Department of Internal Affairs.
Local residents, representatives for organisations, and lobby groups were also present.
Parties, or their counsel, spoke of their support of the two-stage approach, and whether they wished to be designated as core participants in the inquiry under s17 of the Inquiries Act 2013.
Although the hearing was expected to last all day, and possibly into today, it adjourned just before midday.
Further hearings will be held in late November and early December.