My experiences with BB30 creaking...
Set-up; Cannondale SuperSix Evo, SiSL2 with Spidering, Cannondale metal cups and also SRAM plastic cups.
I have had two creaking issues.
1. After a season of hard riding, I was getting a creak which would happen when I pushed hard, whilst standing. I swapped the original Cannondale metal cups for an SRAM plastic cup BB (slightly heavier, but whatever. Problem solved).
2. I got a new frame (Di2 Evo), and swapped my SiSL2 cranks over. After riding a while, I would get a weird, kind of rubbing / creaking sound when my right foot was at about 2 o'clock on the stroke, like when you step on a creaky floorboard, and it depresses with a creak, then resets with another creak. Amusingly annoying. I could only get this to happen when I was pedalling with both feet clipped in though, and not only the left, or only the right, so pinning it down to a particular side from the noise alone was impossible...
Took the BB apart (which was a new Cannondale metal cups thing that came with the new frame), and had a look at all the parts involved.
-Crank arms were fine, with no signs of wear / mis-tightening
-Cups into frame were straight
-Spidering was perfectly tight on the crank arm
The axle though... had a patch or wear on one side at the point where it interfaced with the non-drive side bearing. Odd. I measured the diametre of the axle where the wear point was, and it was slightly less than what it should have been.
I had a good old investigation of everything, and came up with the following theory;
There was not enough compression washers on the non-drive side, meaning that the bearing system was not functioning as intended, which was allowing some coaxial movement of the axle in the bearings. Due to the non-drive side being the side that is not locked into place, essentially being the 'adjustment' side of the system, it was here that the play was manifesting itself. This means that the axle was being allowed to move inside and rub the inner bearing race, which due to my pedalling style, had caused the wear patch to occur.
Solution; buy a new SiSL2 axle (which was surprisingly cheap, giving me the impression that this is designed to be expendable), and put some more washers into the system until it was compressed enough.
This fixed it, and it is now silent (although I have jinxed myself with this post and the bloody thing will start creaking again the minute I get on the bike next, mark my words)