I take it that the financial part is separate to the trade part and that financial services are more important to the UK. Carney is saying to the EU that they need the UK. The EU hasn't commited itself to anything. Carney says they should do so or face the consequences. The financial side has nothing to with what is being argued about with Barnier at this stage.
The UK banks need 'passporting' or banking licenses in the EU. The EU needs a solution to the clearing system and it's regulatory supervision by a third party country which is not allowed under existing rules as London was always in the EU. No one envisaged dealing with third party countries. So, the rules have to be changed as suggested in my link. There will be some form of trade off as no one in the EU or in the UK is going to wreck the other side's financial system. They would be harming themselves. But, as I said, this has nothing to do with the Irish border or the possible collapse of the UK government through Brexit infighting between the various minority factions.
Everything is interlinked.
The derivatives market is massive. Bigger than we could all imagine. Each type of the market is massive.
Can you imagine how massive the section just based on oil is? How many companies would like to safeguard themselves against the price of just oil?
So what do you think is put up as financial structures to combat whatever the risk is for whatever is being bet against?
Yes shares are a large part of it.
To dumb it down and simplify it let's try an easy one. Oil. If your company depends on the price of oil and the price going up would hurt it then derivatives are a good answer. Maybe a mix of shares in oil companies as their shares should go up with the price of oil. Then add a bit of interest rates in with it. Maybe purchase assets to do with the oil industry. Add a bit of whatever currency that normally goes up with the price of oil.
That is the easy part.
Then you need to work out how much is needed to offset the price where money can be made whatever happens. Some are for short some are for long.
Or would you like the more complex and more precise explanation?
But whatever happens yes shares are involved.
And the EU has it all in hand and will be ready to go at the start of next year if needed.