Actually, this news information is a bit inaccurate. Since the late 1970s women could serve in long-range missile units (e.g. Pershing), which are Field Artillery units. They could also be in FA units as surveyors. I had women officers in my FA basic course in '82. They just could not be assigned to battalion or lower cannon units. So, you could have them at FA Brigades. So, we've had women in the Field Artillery for a long time. (Even longer if you count Molly Pitcher.)
Also, starting in the late 70s, women could serve at combat brigade level; in the mid-90s the Assistant Brigade S2 in my infantry brigade in the 10th Mountain Division was a woman. Also the MP Platoon leader attached to the Brigade was a woman.
Now, women can be assigned to battalion and below FA units; the women to which you refer are in a MLRS unit.