Fast Olympic to 140.6 in 3 months?

The training to do a full ironman can be very easily modified to prepare you to do a fast Olympic race three months earlier. 

I was first place overall at a Sprint Duathlon last October and then followed it up with a homemade self-supported 70.3 a month later.  The 70.3 was not for time.  It was just to finish as a consolation for canceled races but it ended up being faster than my slowest 70.3 and I got a PR on the swim. 

You can do something along the same lines as what I did on a bigger scale and be successful. 

At that weekly volume, you're probably better prepared than a lot of people are. 

That's enough swimming and cycling for a full, provided to concentrate some into longer sessions.  You're probably a little light on the run but if you're not pushing hard then just be prepared to walk a bunch.

Yep, you should be fine.  You'll have plenty of fitness from 16 hours/week.  You'll probably just need to change the duration/intensity of your s/b/r training sets.  Don't forget nutrition.  Your run will suffer if you don't absorb adequate calories.