Hi the esc you have do not have a power out to run the receiver which then powers the FCB so you need power a BEC only does power at a preset volts and amps this will run the receiver etc
the E300 was made for the DJI flame wheel and that has a built in power board , others can use system but need a power board or loom for the ESCs I have not heard any thing on that about can only be used with Naza , it makes sense as the Naza has a BEC that comes with it so get over the problem your having
It is also used for an upgrade to the power system the phantom etc have , but at the end of the day its just an ESC /Motor that are a matched unit , the plug still has it signal lead so should work with any FCB , you just need to power the receiver and FCB to make the system work