Hmm, it's getting like that old favourite record, it comes out every now and then.
So, did Spike know?
Darla knew, she was fairly good friends with Drusilla, and Spike to a lesser extent. So the chances are she may have mentioned it at some point in the 90 years or so to Drusilla ( Angel and Darla were together for about 150 years. Angel is about 244, so that leaves about 90 years.)
Another way Spike could have known was that Drusilla may have told him.
You then go into the, ' are vampires psychic? '.
In many films and books vampires are said to be psychic. Why? Well the easiest explanation of that would be due to vampires being not of God, and that having psychic ability was an affront to God ( Drusilla was told that prior to becoming a vampire. )
So it stands to reason that Spike knew that 'Old Uncle Tom' had a soul.
Then there's the thing about Spike being a vampire and him being psychic himself, to a lesser degree.
Then we have the issue of what is canon? Do you believe in canon?
Odd really, 'cos canon refers to something being the truth according to the bible.
This, in a TV show about ungodly creatures written by a person who doesn't believe everything about the bible.
But I digress, canon is said to be what is in the TV series. Yet in the TV series the master states quite clearly that he has a soul. And yet it appears there are those who do not believe the master had a soul, and with that being in the series, it should be canon, so what is canon?
Most things do have an answer, it's just that there are those who do not believe the answer. Canon or not.