Mike they are a known environmental weed across southern Australia - so worth getting your trusty mattock out. see https://keyserver.lucidcentral.org/weeds/data/media/Html/amaryllis_belladonna.htm
They are a bit close to obviously planted shrubs outside the property line so I might leave them until they cross the track. City Services or Parks should have an education program warning about environmental weeds alongside reserves and open spaces.