Yes you can run them together and many (most?) do that.
You might want to get BC/IC Crossover Mod too to get converters between IC and BC power networks.
I have a problem trying to use MFFS containment for my breeder reactor.
The breeder i run is neutral (heat should be stable) and requires full water cooling outside. The problem is that once blocks of water in the top layer evaporate the MFFS containment field doesn't replace them, and i have no way to get them into the field.
I've set it to shut down once heat goes above 9200, and flip the shield off and back on to regenerate the water. But that's sub optimal (cooling back down takes time during which the reactor is stopped, and once it turns back on more water evaporates and the process starts over) and dangerous (if something else unexpected fails, turning off the shield on a reactor that's about to go orbital seems like a bad idea lol).
It would be cool to have some upgrade that could regenerate water blocks, or an option to make the containment field bigger so that water source blocks could stay outside the 5x5x5 area...
Forestry is really cool if you want fully renewable power generation.
I'm currently playing in a legit world, with IC2, BC3, BC/IC crossover, Forestry, logistic pipes (and some other unrelated mods).
I have a fully automated, self sustaining setup with 2 peat bogs, a wheat farm, 2 tree farms (one with rubber trees) and 2 apiaries.
Everything forestry-related runs on peat-fired engines, those 2 bogs are enough for everything and some peat is left over.
Excess wood is converted into charcoal then burned in 4 generators together with excess peat producing constant 40 eu/t.
Then all the saplings are shoved into 2 fermenters -> 1 still to produce biofuel (the one in forestry, not the one in IC2). The fuel is used to power 3 combustion engines for the fermenter/still setup, 6 combustion engines for lasers (BC assembly table) and 4 engines feeding power to a petrochemical generator (BC/IC crossover mod) producing ~12.5eu/t each... and then i still have some leftover lol. All the cooling for those engines is handled with 3 BC pumps powered by peat engines.
So the current setup produces ~90eu/t being fully self-sufficient and renewable.
If i switched those extra 6 engines running an assembly table to EU production i could get ~165eu/t.
Petrochemical generators are a bit overpowered, but the alternative is Bio generators from forestry that i feel are stupidly underpowered, for comparison, from 1 bucket of biofuel:
A bio generator produces 20eu/t over 1000 ticks (20k EU)
Combustion engine -> petrochemical generator produce ~12.5eu/t over 40k ticks (500k EU)
Used purely to power buildcraft stuff with a combustion engine that bucket would produce 5MJ/t over 40k ticks. (200k MJ)