The short answer to OP is that yes, it is possible most years. As for it being ridiculously hard, that is true - but then you must also keep in mind that we're talking about a 99.95, being in the top 0.05% of your age cohort in the State. It is only natural that it's ridiculously difficult. Last year, when the aggregate cutoff was 209.9, we would essentially be talking of four 50s, and your bottom two subject (scaled) scores adding up to 99.
It does make it a lot easier if you are doing a subject which scales above 50 (and you hit that score), that's for sure. For every subject score above 50, it alleviates from the required score at the other end.
One point which I think is important to raise is that, despite only been .05 of a percentile, there is a significant difference between 99.95 and 99.90, as well as between 99.90 and 99.85. We're talking about (on average) two or more aggregate points here, which is a difference of a whole percentile at lower ranges (same difference as between 89 and 90). People certainly miss out on courses by this much. It hurts, but such is the system - you have hard caps, and so you need hard cut-offs.
Some languages only scale to 51 or 52, which isn't the "massive OP bonus" most people expect.
Out of the 50 or so LOTEs, there are only half a dozen with "large scaling":
| Chinese (SL) | max SS | 54 |
| Chinese (SL Advanced) | max SS | 53 |
| Classical Greek | max SS | 55 |
| Hebrew | max SS | 55 |
| Korean (SL) | max SS | 53 |
| Latin | max SS | 55 |
Scaling Report 2012
BUT, I strongly suggest you do not choose these language subjects just for the scaling. You will be competing against a very strong cohort of year 12s. In those 6 subjects the average SS are between 40-45, so a lot a competition. I know a lot of friends that did Chinese from a Chinese background and they didn't go that flash
The same for spesh, to anyone reading this post please never choose a subject based on it's scaling!!! You have to do well in order to get the scaling... or you'll just be wasting time and be at a disadvantage.
I can only reinforce this so much. Taking Hebrew for example - a study I'm obviously familiar with - over half of all students taking the subject are native speakers. The rest are almost wholly advanced second-language speakers, quite often with a Hebrew-speaking family. Although the circumstances are presumably slightly different for each one, each of those studies is an incredibly competitive one, and that is reflected in the scaling. If you speak one of these languages, great, go right ahead and do the subject. But don't just pick it up thinking that you're going to get 50+ or even 40+ scaled, because that, quite simply, is entirely unreasonable.
I'm a bit confused as to what you said about the average SS being 40+, though. Do you meant the scaled score? (Also, since there are no 50s in most of those subjects, the maximum score may be a point lower than the one Alwin wrote.)
Since spesh scaling works slightly differently than other subjects, I would recommend doing it for the marks if you are strong mathematically. Actually, I'd generally recommend doing it if you are interested in maths and are looking to do something in university that is relevant to mathematics.