ORIGINAL: dynoflux
Most speed controller BECs output regulated 5 volts for receiver and servos; if they are connected in parallel (standard Y connectors) the output is still 5 volts. The only problem that could arise from parallel BECs is when output voltages are not close enough to each other causing regulators to fight each other to try and maintain their output voltages. This the same reason you would not parallel two batteries with different battery voltages or levels of charge.
Ok, well in this instance, then unless an esc is spcifically labled as capable of working in parellel like the CC's, then I'd have to assume they would not work anbd would fight against each other unless BEC wires were cut on at least 2 out of the 4