Hi Michael,
I haven't tried this yet, but I'd do the following on a couple of Windows computers to find out:
1) Hack the registry (HKCU>Software>Microsoft>Windows>CurrentVersion>Explorer>Shell Folders) to relocate the "My Pictures" to a network share
2) Install LR, which will install the LR database in the "My Pictures" folder, which is now on the network
3) Install LR on another PC, of which the registry has also been changed as in step 1
4) Make sure that all your photos also reside on network shares
4) Do some work on PC1. When importing pictures, refer to their network share locations, preferably using UNC references.
5) Open LR on PC2 and see if the changes are visible. If so, change something.
6) Open LR on PC1 and see if the changes of PC2 are visible.
If all goes well so far, you can work in either PC, but not yet simultaneously. I don't know enough about the SQLITE database which is used by LR, how and if it supports concurrent users, and whether LR is created as such that concurrent access to the db is allowed or not. Trial and error would be the way to
.
HTH,
Cheers,