Hello Miro,
many thanks for your reply and suggest...yes, this is true ... how you can see we have comment above:
__"If you are still in the same tick, for example immediately after Buy now, then the Ask is the requested open price. But I'm not sure about that... maybe the value of Ask will be updated on-the-fly. I never tested that"[/quote:1e8rg793]
The ASK or BId are the price of the EA when the "internal signal" occur , we are not sure that is the same that read the broker when receive the request. For example for internet latency between the MT4 and broker or for busy line in Internet.... 1 second with volatility can be 10 -20 pips from the ask/bit of EA and the price request of broker.
I think that the slippage value of the fx dreema block is sending to broker with the request, the broker decide to open or not the trade but I think they do not send log in case of slippage and "no trade" (I'm not sure... I'll test it!).
Some serious Broker send the log of the request with price of the request and other log for the open trade at the real price ... but in the last time I don't see it. Time ago I have see the "slippage" alert in the same trade log!
For example this is of yesterday, for pending order there is the price (because is the price of the pending) and the slippage was of 8 pips, for direct trade there is the request but no price (the request was already in the broker server before of the pending!!) .. the trade is opened with 7 second of latency and more of 60 pips of "slippage" or "broker delay" ...I do not know why! ...7 second and 60 pips to find liquidity maybe is too much!! ...
.. this is Pepperstone! 
0 13:29:01.663 : order buy market 1.00 USDJPY sl: 0.000 tp: 0.000
0 13:29:01.820 : order #13444246 buy stop 0.30 USDJPY at 100.452 activated at price 100.540
0 13:29:08.581 : order was opened : #13444643 buy 1.00 USDJPY at 100.901 sl: 0.000 tp: 0.000
I have request to send me the full file log from the broker.
If is not possible to get the price of the request (from broker) the last solution is the ask or bit from EA. Moreover is very interesting to see in the chart the price of the signal too.
I test in the next days. 
Thanks...Regards!