OK, thanks for the explanation.
The answer to your first question is "maybe, but likely yes." At issue is the nature of the equipment. First of all, if it is primarily heating, with no motors, then watts will equal volt-amps (or VA). If it has motors, then VA is higher than watts. More info would be needed here.
The answer to your second question (about the 50 amp breaker) also depends on the equipment. The specs may call out 48 amps, but will it operate at that level "continously," a term that to the NEC means for more than 3 hours at full load? If so, you need to calculate it at 125% of that 48 amps (or 60 amps). But I suspect it behaves like a warming table or dishwasher, in that it cycles on and off or cycles at lower load than higher load, so that it is not at full load for 3 or more hours at a time. In that case, you would not add that extra 25% to the 48 amps.
Your third answer is that whenever you get the value of total load, you do assign it equally to all three phases (3300 VA each, in your question).
One last point: if the specs allow for any voltage from 208 to 240, at what voltage will the equipment draw 48 amps? My guess is that 48 amps applies at 240 volts. In that case, the current draw if it is supplied at 208 volts will be lower, as will its power draw. For example, a warming table would get as warm, if you run it at the lower end of its allowable voltage range.
Now I have a question. What is your voltage source? Is it single phase 220 volts? Is so, you don't assign 3300 VA to each of three phases, as you don't have three. You would assign 4950 VA to each of two phases.
