Dave, AIP ENR, General Rules and Procedures,
41.
CIRCUIT INFORMATION, SEPARATION MINIMA AND HEIGHT
41.1
Circuit Information
41.1.1 Pilots should fly a circuit commensurate with the aircraft type they are operating. However the use of any circuit procedure does not alter the responsibility of each pilot to see and avoid other aircraft.
Pilots operating in the circuit should manoeuvre to follow traffic ahead of them in the circuit.
48.7 Joining on Base
48.7.1 Joining on base leg, whilst not prohibited, is not a recommended standard procedure. CASA recommends pilots join the circuit on either the crosswind or downwind leg. However, pilots who choose to join on base leg should only do so if they:
a. have determined the wind direction and speed;
b. have determined the runway in use;
c. give way to other circuit traffic and ensure the aircraft can safely (no traffic conflict likely) join the base leg applicable to the circuit direction in use at the standard height; and
d. broadcast their intentions.
It would seem that 'oldmate' that cut you off was either inconsiderate, unaware or just deaf blind and stupid.
As a general practice, is joining on Base leg safe of advisable? Yes, as long as the rules are heeded and commonsense prevails.
Good Luck with the training.