bruno,
according to lcr/README file
A gateway matches
a request if user part of Request-URI and "From" URI match the
prefix and From pattern of the gateway. Matching gateways are
then ordered for forwarding purpose (1) according to longest
user part match, (2) according to gateway's priority, and (3)
randomly.
so if you have one lcr entry with sip:123@.* as from_uri regexp and
another lcr entry with empty from_uri, and call comes from 123, then
both of these entries match if their prefixes match and the one with
longest prefix will be selected of if same length, one with priority.
i'll add a note about empty from_uri entry into README.
-- juha