10oz bars removed from perth mint bullion site, page-26

Of course it's not guaranteed that they'd do so.. But it's free riskless money, and that's what arbitrage desks exist for :S.

Why do you assume it has to do with blackrock? The arbitragers compete against each other, and the group ultimately taking the trade would simply be the ones who can get silver bullion the cheapest and quickest to the ETF trust to be issued new SLV shares to cover their short positions.

The only reason they wouldn't is if they couldn't get their hands on physical at spot prices in which case we might witness SLV trading above NAV which didn't even occur when silver was at $50/ounce.. Till then, point dismissed- physical silver exists at spot price.
(just not at the Perth mint or eBay)
:)