A "sources" story from Reuters
ECB would pledge to backstop markets in the case of a UK vote to leave
Would announce a commitment to maintain market liquidity
Would work in tandem woth the Bank of England
Any announcement on backstops or action would come June 24th (day after the vote)
ECB and BOE would open unlimited EUR & GBP swap lines
The senior ECB official apparently spilling the beans says there would be a statement to do whatever it takes to maintain adequate market liquidity.
It shouldn't be a surprise to anyone really but the Euro looks like it might have been shaken by the headline. We're back towards the lows and trade at 1.1217.