Well, the fact that the BCB is attempting to prop up its exchange rate with derivatives is an indication that it's more interested in preserving the comprador class' access to foreign consumer goods than in domestic stability. If the Real is sliding it should let it slide, precisely because it needs to preserve its reserve buffer. It is possible that this all has something to do with the 2014 football world cup and the 2016 olympics. After that, all hell might break loose in the domestic market and the swaps might explode in the BCB's face.

A society committed to the notion that government is always bad will have bad government. And it doesn't have to be that way. — Paul Krugman

I suppose that's the point the FT article is trying to make:

... Gersztein and Alday at BNP Paribas think a reasonable indication of the cost is to net out the central bank's short dollar position through currency swaps from its foreign reserves. After all, it is not only the stock of reserves but also the broader health of the Brazilian economy that affects its ability to pay its debts.

(my emphasis)

That is something investors may wish to keep a close eye on if, as widely predicted, the real continues to weaken and Brazil's fiscal position continues to deteriorate during 2014 and 2015.

A society committed to the notion that government is always bad will have bad government. And it doesn't have to be that way. — Paul Krugman