This is incredibly short-sighted thinking on these environmentalists' part, in my opinion (HCN, 10/10/11).
It's called the southwestern willow flycatcher, not the tamarisk flycatcher. This is a bird that needs willows and insects to survive. Part of the reason tamarisk is so invasive is that almost nothing can eat it. Releasing the beetle means two things: more potential food and more habitat for the willow flycatcher. Allowing tamarisk to continue to spread means continuing degradation, probably until the flycatcher is extinct.
The beetles are doing their job in the Great Basin, but it's questionable whether or not they will make it to the Owens Valley in a timely manner. Most likely, by the time they get there many of the native willows and other species will have already been crowded out and it will be too late.
In the long term, removing tamarisk will do little to ease the West's horrible watershed problems. It's a step, though. I think it's an important one, myself.