It seems that emc was not the high priority for the esc guys. I can measure high ringing at the esc terminals at every change of pwm (falling and rising). At full throttle pwm is 100%, so ringing is only at motor commutations. I tested without mounted Amb transponder and the noise is still the same at loop amplifier. Unfortunatelly all of the tested esc shows the noise, overall I checked 7 different escs.
The frequency of the noise is below 1Mhz, do you think it would be possible to add some filter?