Some might remember WW did have use of one A319 and one A321 a few summers back - this was when WW operated about 6 (+2 BD frames) from MAN. I don't think there is the capacity at mainline to lend WW frames. Even at the weekends, as BD tend to send the short haul aircraft on charters and use the ERJs on the domestics. Unless BD pulls down a lot of the mid-haul flying over the next 6-12 months, BD frames operating for bAby is unlikely.