Mounting system rw from system app

Hello everyone!

I'm playing around building my own version of Cyanogen and I have a question for which I couldnt find an answer. I'm trying to copy new keylayout file to /system/usr/keylayout from my app. The app is being built with ROM and copying works when I ask for root permission and grant it. Is it possible to do the same operation from my app without even asking for root permission? Can a system app mount /system as rw?

Thanks in advance!