The ACT is essentially just Canberra, so if your results show a trend towards inner cities voting yes and regional areas voting no then a population that’s almost entirely city based voting yes doesn’t seem too unusual.

What they don’t mention but might also be a minor factor is that a large percentage of Canberra works for or with government, so another government funded body is less likely to be a turnoff to ACT voters as it would be to the rest of the country.