Find specific apps by name, getting their version, via command line
A solution using mdfind and mdls as a one-liner:

mdfind "kMDItemCFBundleIdentifier == com.microsoft.Word" | while IFS= read -r path ; do echo "$path"; mdls -name kMDItemVersion "$path"; done


This would print (if both Office 2008 and 2011 are installed):

/Applications/Microsoft Office 2008/Microsoft Word.app
kMDItemVersion = "12.3.6"
/Applications/Microsoft Office 2011/Microsoft Word.app
kMDItemVersion = "14.6.9"


That's good enough for my needs. I still wonder if there's a way to get the information from lsregister or a similar tool that looks into the Launch Services registry.