Excellent map.
Only the explanation about changing from right to left hand traffic beyond Waterloo is highly dubious. Actually, I had never read anywhere (not even in official documents) that it was ever intended to transfer trams from the coast to Charleroi. Furthermore, it could be possible to broken out the junction and simply driven on the right, as on all other routes: middle platforms are used almost everywhere on this system.
These branches should have come into service as early as 1985, but the then remaining tram operator (SNCV/NMVB) could not reach an agreement with the other operator (STIC), which had the monopoly on public transport operation (but only with buses) in this particular area.
During the planning, the STIC was effectively involved and demanded that boarding would be done on the right, analogous to what happens with buses. Their travellers were so familiar with this and there was no reason for them (the STIC) to change it...
In 1991, both companies merged but it's clear for everyone that it would take many years before everyone could share the same offices...
The STIC's specific desire didn't disappear in a one-year span and so for the sake of peace, left-hand traffic was inaugurated in 1992, as it had been planned long before...