Hi,
A friend is looking for a Earth Leakage Circuit Breaker wich can be controlled remotely.
Any experiences / sugestions?
As an certified electrician I have only one advice, before you start with something like this.
The idea of such device is to prevent electric shock and injuries, maybe even death, caused by a faulty device in the circuit.
It is highly important, that after such device trips, the circuit behind it gets inspected, and the reason for it to trip will be found and eventual faults are fixed, before the breaker is switched on again.
I can only demotivate you to try to automate such device to switch on again without such inspection made.
In a good working installation this device will NEVER trip. If it does, you need to find the problem and get rid of it.
Please do take this advice seriously. 
If you persist on switching the circuit behind the leakage breaker remotely, use a remotely operated contactor installed behind the breaker instead, leaving the leakage breaker untouched. Much safer.
Non-MEN power systems can become unbalanced for all sorts of reasons that aren’t related to an earth fault. For example, in Malaysia ELCBs nuisance trip when thunderstorms passing overhead raise the earth potential.
I was asked to design an automatic recloser for an ELCB with ever increasing back off delay for use in remote communications sites that suffered from this.
After protesting about exactly the issues you raised the project only went ahead once an interlock that prevented reclosing the ELCB was included. This was to be tripped by personnel opening the site door and had to be reset from the outside.
The project was eventually dropped for other reasons and I’m kind of glad it never went ahead.
It is a bad idea.