Yes, it is possible.
After fussing and worrying about finances over the past couple months (long story), I was talking to some friends who told me that the CAF owed me money since I work part time. Did you fill in the paperwork they asked. Do you get your allocation they asked. I thought I had, but after some very thorough research done by a good german friend who lives in Paris, I realized that indeed I was missing out...and the CAF owed me back pay for benefits I should have been getting since February 2010 when I returned to work after Max was born.
So manned with my best French , copies of all the documents I'd sent, dates, amounts, and my personal access code (since it's all automated by phone) and a hell of a lot of patience, I called the CAF. After going through the spiral of their phone system, I finally got a real person.
Four minutes. That's all it took. I told the CAF lady that I haven't been getting my allocation. I told her I submitted everything by hand and they owed me money (the only way to get things done in Frence administration is to assume you are right, even if you know you're not). She didn't even have time to put me on hold. she pulled up my file, said she had scans of the documents I'd submitted and yes they owed me 16 months worth of back pay. The reason, "le technicien a du zapper" (it must have slipped the clerk's mind). Oops.
That makes three positive French administrative experiences in only 3 months. The winds of change are in the air....
For other working moms, if you want to know your rights, have a look at this link: complément de libre choix d'activité. It gives you information on what types of allocation you will get