They are not!!! merging with Chubb and moving head office to Ashfield is the TOTAL extent of it.
This was United Technologies Corporation's ill-fated "UTC Building and Industrial Systems" aka BIS where they tried to bring Otis plus all the other commercial companies like Carrier and UTC Fire & Security under the BIS label. The idea was that there was some degree of synergy to be gained by offering a more one-stop-shop, primarily in the commercial building space. The formation of UTC BIS was announced in 2013, but by the end of 2016 Otis and Carrier were separated again with Carrier and its related businesses as UTC Climate, Controls and Security (UTC CCS).
In 2018 UTC announced their intentions to spin off Otis and CCS into Otis Worldwide and Carrier Global, and this was concluded in April 2020, with the remainder of UTC (which was all aerospace) merging with Raytheon to create Raytheon Technologies (stock ticker RTX)
As far as Otis Australia's operation, they now exist as a subsidiary of Otis Worldwide, with their headquarters offices on Level 23 of 363 George St in Sydney.
And, so far, no talk of them leaving Australia any time soon ...