Given sucky weather, short daylight, and work schedule...I'm indoors. Question: does one hour before work and one hour after equal the training effect of 2 straight hours? Not including warm up/cool down and same level of effort. 2 straight hours on the trainer is mind-numbing and a scheduling pain for all those around me.

Unfortunetely, they are not the same. It takes a different form of endurance to work for 2 hours straight as opposed to 1 hour. This applies especially to endurance sports such as cycling.

The one advantage the 2 workouts of 1 hours has though is that you generally can work harder for that shorter period of time then you would per hour for the longer workout.

Yeah, two different kinds of workout. You can do 2 sessions of intervals or high-aerobic workouts in 1-hour each. That won't be the same as doing 2-hours straight, which is a short-endurance ride. And yes, warm-up time is a factor here as well.

If you're slightly tired before your second workout does it make it equivalent to 1.5 hours then?

Since exercise (as well as sleep) causes your body to release growth hormone, you can benefit from training twice a day since you will get a double dose of growth hormone. And if you take a nap and sleep, you can get your body to produce growth hormone 4 times a day. So ride your bike and take naps!