the ecb is the governeing council as such, it is made up of the member state banks, and as such would have access to their reserves. It kinda goes both ways, as in the irish c.banks borrows and lend to the ecb by borrowing and lending to other euro c.banks.
At the inception, the irish c.bank would have had x amount of money, This x amount has now grown in by an amount xreturn rate years. It has also swelled by the money multiplier (due to the fractional banking system we use). The Central banks lend money out to retail/investment banks and governments in return for interest. They also hold certain collateral obligations and reserve requirements. This money is also lent in the overnight markets, with the orignal banks earning money, albeit at EOINA (small interest rates). All guaranteed by the c.banks.
Yes, alot of these reserves are spread throughout the euro area, but this money is not kept in the c.banks but re-dsipersed back out to the market. It’s this dispersion that provides the diversification.
An analogy.
I get 100 euo from you and and pay you small interest. I take this money and lend it to you ten of your friends. Your friends are then all required to give me back 2 euro each for me to hold on the back that they can use the remaining money to make loans. So I have 20 in my pocket, and the lads have 8 each and 80 total…They repeat this process and loan all the money to another bank, this bank has to deposit a certain fraction with me, “rinse and repeat” this cycle…
You look for your money and i call the lads, they pay up, even if only 8 pay then i still have your money. (actually less than 8 with interest spread being earned)…of the two who don’t pay, they would have some of thier money in the calling banks accounts so the orignal bank could net it off, and adjust their Collateral trades…
Its basically a whole case of dillution. Yes, there is risk, but this risk is spread out far and wide. The cbanks act somewhat as a market maker and lender of last resort. They can always honour a debt, all they have to do is print money. Of course this printing process is tighly controlled to supposedly track the interest earned in these collateral accounts…
that is no doubt badly typed and spelt, but excuse the rush.