That trail looks like it should be a fun trip.
Here are my thoughts, FWIW.

Are you planning to commute year-round? in what types of weather? Your road bike may not be able to fit (or mount) fenders, which are invaluable in rain. Commuting bikes often take a beating - are you willing to risk it getting scratched, accumulate a lot of drivetrain wear, and generally take some abuse?

1. tires:
Check the brake clearance and ask your LBS if you're not sure something will fit. The fit of an individual tire can vary quite a bit from the marked standard size. If you plan on commuting in snow (if that were my bike, I'd baby it too much to even think about snow/salt), you want plenty of room to avoid snow buildup and super-frozen brakes. You might want to try a tire like the Schwalbe Marathon Plus, which is available in 25 and 28c. Touring and cyclocross tires will both offer more tread than standard road tires, but 'cross tires may be overkill for your commute.

2. weight:
Will you be carrying any clothing, documents, commuters, or other supplies with you while commuting? The weight of all those things (and carrying devices like a rack and panniers) adds up fast. You could get different wheels, but for commuting I for one care more about durability than weight, and actually prefer to ride my heavier bike for most purposes. Think of how light and fast the Scott will feel after riding your other bike consistently.

3. handlebars:
STI would be awkward on mustache bar - lay your bike on its side, place your hand in the curve of the drops, and try shifting. You'd need to find a way to reach in and move the little levers up and down under the brake levers - and they wouldn't be at your fingertips all the time. Anything I envision for hoods + horns would look crazy and feel wrong. There's a reason those designs are used on singlespeeds a lot more often than geared bikes. Are you interested in them for comfort or design reasons? Drops offer a wider variety of hand positions than bullhorns, and mustache definitely fall in the try-before-you-buy category. If you're worried about control issues on the trail, remember that 'cross bikes have drops.

4. others:
Saddle comes down to personal preference. Does the seat post need replacing? Saddles and mounting brackets are pretty much universal.
If you're accustomed to clipless pedals, why not just go with what works rather than using toe clips? If the seatpost is in good shape, I'd spend my money on a pair of shoes with walkable soles instead.

All in all, your bike would take some accessorizing to be a 4-season day-in, day-out commuter - at least here where we get snow and ice. If you're planning to commute occasionally there's nothing wrong with it, but it's also perfectly usable as is (assuming good mechanical condition as you describe). If you get more serious about commuting or your preferences change, then it's time to make room for another bike in the stable!

happy riding.