Unfortunately all the details are on their prospectus but it's only in Swedish.
I do remember reading somewhere that every note would be backed by coins so maybe it's not quite an ETN.
"XBT Provider AB will hedge all sales of the bitcoin traded note by buying an equal value in the bitcoin market."
http://www.coindesk.com/swedens-nasdaq-exchange-approves-bitcoin-based-etn/From wikipedia -
"When an investor buys an ETN, the underwriting bank promises to pay the amount reflected in the index, minus fees upon maturity. Thus ETN has an additional risk compared to an ETF; if the credit of the underwriting bank becomes suspect, the investment might lose value, the same way a senior debt would."
"ETNs don't actually own anything they are tracking."