can i use ingame maps as a template and how?

Hello I am a massive fan of the ballistic gamemode and I come from counter strike where many people use the in-game maps as templates for practice maps. I was wondering if there was any way to grab the skyline 10 map and edit that using the editor to make utility and prefire practice maps for myself and the community. I see one creator has a greybox version of skyline 10 and I figured if he found a way to get the map files there is a way to do it.