Gas/hybrid buses get lower mileage than diesel
 

This is from 3 years ago:

Long Beach Transit: Two-Year Evaluation of Gasoline-Electric Hybrid Transit Buses

Long Beach study shows gas/hybrid buses get lower mileage than diesel - AutoBlogGreen

Study Finds Fuel Economy of Gasoline-Electric Hybrid Buses Lower Than That of Conventional Diesel - Green Car Congress

In the meantime, Volvo introduced a diesel/hybrid bus, which is claimed to reduce fuel consumption by up to 30%. Of course, diesel-hybrid technology is more expensive than gas-hybrid or straight diesel, but allows not only lower fuel consumption, but also lower CO2, NOx and soot emissions, which is just as important in an urban environment.

Are they accounting for the greater energy content of the diesel fuel?

Electric buses with overhead power lines are far more efficient than diesel.

I am surprised they even made gasoline-electric. Really would have guess they were diesle-electric or even CNG-electric.

Why of course? I'd think it'd be just the opposite: bolt the same hybrid parts to a gas engine or a diesel engine, same cost either way.

Diesel engines cost more. Still, from a fleet maintenance standpoint, I still would have expected diesel-electric.

Its not that the diesel hybrid parts cost more, just the diesel parts. This, in turn, makes the cumulative costs go up.

It was just an irresponsible way to word it, which makes it seem like the better candidate is unbearably expensive.

Yes ... but it changes the results to the opposite of the original poster's title ... in all 3 posted links the Hybrids are more energy efficient ... see bellow:

In this referenced paper it states:

It goes on to compare based on fuel costs ...

The Diesel fuel was cheaper per gallon by enough of a margin to keep it cheaper to fuel per mile.

But it goes on to also look at the maintenance costs of the two:

The diesel fuel per mile saving are not large enough to compensate for the higher costs to maintain them... although the diesels were older buses ... The hybrids were newer ... a better comparison would have been between two groups of hybrid and diesels that were equally old / used.

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In this has the same findings and states:

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Also seems to have the same findings:

Gaseous fuels such as CNG or biomethane make more sense for an urban transit bus than gasoline.

Agreed! Urban transit vehicles (a) seldom drive away from home routes to far-away places and (b) always return home to their maintenance depot each night...making "refueling" from a SINGLE location a strong point.

I usually point biomethane as a possibility to increase the availability of gaseous fuels in the countryside, since it's renewable, can increase the income of farmers and has a lesser impact in the availability of arable land for food and industrial feedstocks compared to ethanol. Then, not just for urban transit, it could also become a viable option for longer intercity routes.

Actually, in some intercity routes in my state, a CNG-powered bus would already make sense, and eventually a hybrid driveline would be interesting to reduce the fuel usage while stopping in certain locations where CNG is still not so easily available.