Truclent, who came up with the initial design, mentioned in the power room thread that the burn value was around 16000, or half of biofuel. This means at full temp a single cell lasts over 50-ish seconds. Basically, at full heat a single centrifuge running the rubberwood should be more than enough to fuel a single 36HP boiler.
Another thing you can do instead of using gas turbines is use a cobble gen to create lava, then burn the lava in the new gregtech thermal generator. It can produce 30k eu a bucket, 10k more than the normal geothermal (unless directly connected to a pump), at 24 eu/t. Really, my major complaint about this version of Gregtech has to do with the quantum tanks. They can store more than a 7x7x8 railcraft tank in a single block, that and they aren't as aesthetically pleasing imo.
But yea, with that thermal gen you can turn 20k MJ into 30k EU.
Now, for the Turbine, I just threw in a single methane cell into one and set it directly next to an ADSU. Interestingly I thought it would have given 50k eu, but it gave 44,992 eu, so there's some loss happening even when directly next to a machine it's supplying. That said, if the 16000 fuel value in a steam boiler is correct, then a single methane cell should produce somewhere around 145k MJ (not doing the math again, the recent solid nerf doubled all the previous values for liquid, and this is half of the current biofuel so it should be half the MJ). Now, at a 2mj to 3 eu conversion....yea, the boiler ->magma crucible -> thermal generator setup is going to produce a lot more than the turbine and at a higher rate.