Two MSs to be featured in this new series can be seen in this previous posting.
The preface chapter, "A Teenager's One Year War" (少年達の一年戦争) is featured in Dengeki Hobby October issue, but being a collaborative project between Dengeki Hobby magazine and Gundam Dot Info, you can also read this chapter (in Japanese) on Gundam Dot Info (requires T-Times Crochet plugin to be installed in your browser first).
According to the introduction, The preface chapter will go back to the early stage of One Year War, in April of UC0079 to tell the story of 3 person trying to cross the desert to reach Mexico after California Base is conquered by the Zeon forces.
Gundam Dot Info will publish new chapter of the series on the 25th of every month.
Images and information are from Gundam Dot Info.