Both these log files are statically set in /usr/bin/emerge. They should be configurable to be in a location of the sysadmin's choosing. The tools that I've looked at that depend on these files can all be configured already to look at a different location for the log files. With the current /var/log/* location set as default, I don't see a reason why the logs can't be made to be configurable. Ref: http://forums.gentoo.org/viewtopic-t-491359.html
Maybe if someone provides a patch