After a quick bit of research I think I understand how the fund does this. It's basically a borrowing-to-invest strategy that's wrapped into a single product so you don't directly see the borrowing. It's also perfectly legal. Given the marketing to high income individuals though, I'm willing to bet the costs are out to lunch on the product itself, but it's easy to replicate on your own if you have some self-directed investing experience.
For example, let's say you open a self-directed Margin Account with Questrade. You will pay interest at 5.2% which is 100% tax deductible. On $250,000, it would reduce your taxable income by $13,000 a year. If you invest the $250,000 into the iShares Canadian Growth Index which yields 0.62%, you would only realize $1,550 in annual tax-advantaged dividend income.
If you earn $250,000 a year in Ontario with no other deductions, you would reduce your annual tax bill from $97,500 down to $91,200. Basically you save $6,000 in taxes, but paid $13,000 in interest. Hopefully the capital gains portion of your investment more than makes up for this amount and you will be better off because down the road when you realize the capital gains income, you will be in a lower tax bracket.
I would certainly consider a strategy along these lines in an undervalued market, but to me it's a little risky after a 8 year bull market as I don't want to be caught upside down on my margin.
Hope this helps.