Most likely a cultivated plant as E. sideroxylon is not native to the ACT. Its natural range is on the western slopes and plains of NSW, and into Qld and Vic.
Hi. This is definitely a planted specimen. It is the same tree as reported in an earlier sighting (37332). Also see Michael Mulvaney's comment at http://canberranaturemap.org/Community/Sightings/Details/37332 There are a group of similar trees nearby.