Hi ,
Please note that IG are still not offering Greek stocks due to the volatility and continuing uncertainty surrounding Greece. Due to this each Greek stock is set to 'Closings Only' which means we are no longer offering the stock and so clients can only close existing positions. We will generally do this if a stock is too small or illiquid.
Having taken a look at Piraeus Bank I cannot see these quick vast increases in price that you refer to, however, there have been a few corporate actions on the stock in the last year or two which will explain the large moves on charts, but we aware these pose no material change to the stocks market cap.
In regards to your last comment, IG is fortunate that we have a vast number of clients and so we can net off or internalise a lot of client exposure as we will have long and short clients. There are of course times when there are more long or short which leaves IG with an exposure to that market, and so we hedge this exposure in the underlying market to reduce the risk to IG.
Hopefully this answers your queries, feel free to ask any further questions.
Thanks,
Michael