ACA 2015 uses the 2013 file format. ACA 2010 uses the 2010 file format. While the program lets you save a 2013 format file to 2010 format, that is only effective for vanilla AutoCAD objects. AEC Objects will not be usable and, the presence of future AEC Objects will disable the AEC features when opening that file in ACA 2010.
If the only reason for doing this is so that someone with ACA 2010 can view the file, you could turn on PROXYGRAPHICS (set it to 1) in the file. That will greatly increase the file size and it will still not allow the 2010 user to make use of any AEC commands. The bottom line is for multiple people to effectively share files in AutoCAD Architecture, everyone needs to be running a version that uses the same file format. Ideally, everyone would be using the same version, with the same service packs applied, but at the very least, they all need to be using versions that use the same file format.
For the record:
Architectural Desktop 2004, 2005 and 2006 all use the 2004 file format.
Architectural Desktop 2007, AutoCAD Architecture 2008 and 2009 all use the 2007 file format.
AutoCAD Architecture 2010, 2011 and 2012 all use the 2010 file format.
AutoCAD Architecture 2013, 2014, 2015 and 2016 all use the 2013 file format.
David Koch
AutoCAD Architecture and Revit User
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