While nothing is confirmed or official, a Ticketmaster Australia page went live this morning with information about U2's upcoming The Joshua Tree 2019 Tour. The site did not provide specific dates, but mentioned three locations: Perth, Melbourne and Auckland. Noel Gallagher's High Flying Birds are featured as the opening act. Further details indicate that fan club pre-sales will begin Wednesday, May 22, with the official public on-sale occuring Monday, May 27. On-sale times vary by location. It is also likely further dates throughout Australasia and Asia will be announced in the coming days.
Another Ticketmaster Australia page went live with details regarding the sale and timings of the Perth, Melbourne and Auckland concerts, and the sale of tickets seems to follow the previous subscriber presale system adopted by u2.com for recent tours.
Please be aware that all of the above information is not official, so take caution regarding its accuracy. Nothing is official until u2.com and Live Nation make the official announcement.