I've found that ticks for equities (for example for companies from US market like Amazon or Apple) someone could name as "best bid/ask offer" (or Level 1 type of tick data) and them clearly not contain "trade bid/ask" ticks. You can see that bid always not equals ask so it is not a "trade bid/ask" ticks.
I've compared candlesticks for 5-mins frame from yahoo-finance and from Dukascopy.com and receive different open/close/high/low values for these candles (obvious result as Dukascopy.com data includes I guess "best bid/ask offer").
There is some warning at the bottom of the site "Dukascopy Bank's CFD quotes shall not be considered as precise price information obtained directly from the exchange and/or the trademark owner of the hedging instrument." Is it connected somehow to CFD product?