No you don't know where the laundered money ends up. See my other longer comment in this thread, but the gist of it is that the pool will use the transaction fee to pay their mining rewards out of, and pay out rewards from previous blocks to a series of separate virgin addresses controlled by the original party in a way that looks indistinguishable from mining reward payouts.

I will grant you that the article didn't fully explain the process, and elided important details.

Most of the "important details" aren't, as far as I can see. The only big thing that the pool adds is plausible deniability: everything else can be simulated by sufficiently complex tumblers; it's just that the vast majority of mining payouts are untainted that gives this a mixing effect. (You can delay payments and pay back in installments to multiple addresses that are not the source address but are owned by that person, via either mechanism.)

Running some numbers, it looks like about 98% of Bitcoin's hashrate seems to be held in the top 10 mining pools; assuming this isn't a common service provided by those top pools then a mining pool which launders too will have, say, 1% of the network hashrate at most. That's actually a nice place to be in; it means you get a payout roughly every 1000 minutes of 25 BTC (~$400) plus what looks like typically 1500 transactions or so paying you about a nickel apiece -- so let's optimistically say you get a payout of $600 total every 16 hours, or $900/day. Maybe you can keep plausible deniability going even when 25% of your revenues come from laundering transactions, so that means they can launder about $300/day. That's not too bad, about $100k/year, but it's not a massive chunk of the money laundering happening worldwide either, which usually is quoted in at least terms of billions of dollars -- so 4-5 orders of magnitude larger. Even considering how much the network as a whole could maybe launder if they were crazy about it (100x more participation in laundering, 10x more revenues from laundering transactions) you're still only 1-10% of total global money laundering by this mechanism before you have no presumption of "most of this money is clean so the laundered money is properly hidden."

So e.g. if you wanted to launder $1m within a year using our example pool then you'd have to pay in $2700/day and the legitimate transactions of the pool would only be 900/3600 = 25%; I'm not claiming that this is insecure -- but rather that a normal tumbling system could do this too, purchasing 25% of the money-to-be-laundered from a BitCoin exchange, gradually paying out over a year, and reselling the surplus 25% back on the exchange, for no real difference in security (but potential gains in speed and volume). If you charge a 10% laundering fee then this is an investment of $250k to gain $350k over the course of 550 installments in the year, so if I'm doing the math right that's a return rate of 0.13094%/installment or a nominal rate of 72%/year -- plenty enough to cover whatever risks there are in the currency, inflation, opportunity cost, etc. So it wouldn't be prohibitively much to ask the laundering network to invest, if I'm doing these numbers right.