What happen if someone will touch 2 electric high voltage cables from different energy supplies?
OMG .. DO NOT DO EITHER....

It is true, if you are isolated from ground or any other way for current to flow, you can touch a power line without frying yourself. However, in order to get up to that voltage you need to be "charged up" first. That can also kill you if the voltage is high enough. 

However touching another cable at the same time from a different source can also fry you if the source is at a different potential or a different phase from the first. 

Since you can never be sure of either of those... DO NOT EVEN THINK ABOUT IT.

Even touching the same cable at different points, say arms outreached can kill you, especially with a.c. cables. The voltage will be different in each hand.

HOWEVER If you are talking about HIGH voltages, you may think you are isolated, when in fact you are actually not.  If you are close enough to a conductive "drain" the energy can pass through you then JUMP through the air to said drain and you will have a very BAD day.

R.I.P. the man in your image.