There is always some truth to every rumor. I do not doubt that it has happened at one point or other but in general I think that this does not happen as often as Fischer might have wanted one to believe.
Is it true that today's professional Chess games are often prearranged?

I would like to refer you to my reply to your other active thread, among many:
http://www.chess.com/forum/view/general/whats-the-proper-way-to-study-chess?lc=1#last_comment
As to prearranged.
Yes - there are many instances where chess players will agree to a draw before actually sitting down to play. There are also many instances where there is a huge ratings difference between two players - you might call the outcome prearranged in such match-ups.

Very few games are pre-arranged. It's like swine flu: a few people die, and billions are talking about it.

sure, he was raving, and probably foaming at the mouth while doing it, but it probably came from somewhere and I wouldnt disregard it. When he played there definately was fishy stuff going on, like people deciding to agree to draws before the tournament even began, and such (and even working out what exact moves they would make before agreeing). Im not insane like fisher but i do share his health mistrust of people. But no I dont think todays games are prearranged nor do I tihnk that could be sucessfully done for long. someone would blow the whistle im sure.
Oh cmon, he said these things when Kasparov was WC, it was hardly "arranged" for Kasparov to become WC, heck, he had to fight an upwards battle to get there. Unless ofcourse, that uphill battle was just theatre aswell, the drama tightens!
Oh and I love the whole "some truth to every rumour", where there is smoke there is fire thing. I guess that applies to his anti-american anti-jew statements aswell then?
Few quotes that came from Fischer after 72 has any merit at all to them, it's just the ramblings of a messed up man.

...of course professional chess games are "prearranged"...someone must decide all the logistics to put the match together...harhar
But seriously, there have been rumours about games in the 50s-70s...where the Russians especially, but not exclusively, would play "team tactics"...ie. agree to draw when they play each other, but fight for the win when they play others.
In today's climate, it still is possible...but the question is "to what end?" In some cases it may benefit both parties to agree to a draw(to proceed to next round)...but in a world championship match like Anand-Topalov...how would this arrangement benefit any of the parties? I don't see it at this level...other than the possibility of it being politically motivated. The problem with any such stuff, is of course...the arrangement is great when we are on good terms...but when this changes...the beans will be spilled.
In any event...I see this sort of thing possible for the Topalov camp...but not Anand's IMO.

Very few games are pre-arranged. It's like swine flu: a few people die, and billions are talking about it.
lol, I like this comparision :)

Fischer made claims that when he was rising through the ranks that the Russians would rig games among themselves in tournaments so that a Russian player would be able to come out on top. Maybe true, hard to say. As to latter comments you have to remember that Fischer was, to use clinical term, completely freaking nuts later in his life. He was a raging racist and anti-Semite, a recluse, borderline paranoid, and predisposed to government conspiracy theories. I wouldn't take much of what he said at that point seriously.

In the 1962 Candidates tournament, there was undoubtedly collusion by most of the Russians to draw their games, and this hurt Fischer. This was a 28 game tourney between 8 players, everyone playing each other 4 times each. The 3 top Russians, Keres, Geller and Petrosian, drew every game with each other with an average of 19 moves per draw. This helped them conserve their energy for the other matches.
I wouldn't be surprised if some of the Russians played quick draws in other tourneys around the same time.
Unfortunately, this all just fed Fisher's paranoia and he probably suspected all kinds of things that didn't happen. At the same 1962 tourney, he accused Korchnoi of throwing games to the other Russians, and this was certainly not true.

I don't feel a quote from the seventies can accurately reflect the state of "today". I'm not sure how broadly you define the present, but I'd say these pre-arrangements are down from the 1970s (the described automatic draws of Russian players among themselves) but up from, say the 1870s (there was less at stake back then, I believe).
In no case would I use the word "often".
Bobby Fischer claimed countless times during his radio interviews that today's top Chess games are prearranged. I know that he was ranting, but is it possible that there is some truth to his claim? I think that at best the guy was paranoid and at worst he was indirectly admitting that today's chess games are so brilliant compared to his that the only way anyone could come up with them is if they are prearranged.