If the Red Belly Black Snake were put in extreme heat it may be able to survive as they consume their energy from the sun, and is able to find a shaded area when to much energy is consumed. If the snake were put into cold conditions it is able to hibernate although if it were cold all year around the snake would be unable to survive.
If the Short-beaked Echidna were put in extreme heat conditions and away from its general warm environment it may be able to withhold the heat, but if were placed in extreme snowy condition it would be unable to survive due to the extreme weather conditions.
The Eucalyptus Pauciflora would be able to survive in inner city, and suburban streets, as it is already adapted to extreme cold, windy and snowy conditions it would be unable to survive in the extreme heat.
Overall:
All of the living organisms above would be unable to survive in their different natural living conditions, this is due to the living organisms above being to well adapted to their natural habitats. and is a reason why they couldn't withstand the different condition that Australia has to offer. Although if there were one organisms that would have the greatest chance of survival it would be the Red Belly Black Snake, as when in extreme cold condition there will be sun that is able to fill the snake with every, and when in winter and there is no sun it is able to go into hibernation.