Nope, not on a child theme or the bp-default.
I’m running Buddypress on a multisite install with subdomains. My main domain is http://www.astromono.com and i have two other subdomains: comic.astromono.com (with comicpress) and saril.astromono.com (with buddypress). When I try to edit the theme that’s on the main domain, I go to Network Admin, look for the theme and then try to edit the main php template (index.php).
Before I installed Buddypress, I got access to the main php template just fine, but now when I try to edit it, I get the Buddypress main php template instead of the one that comes with my theme. This issue was happening before I installed and used the BP Template Pack in order to make my theme compatible with BP.