Not accurate, i have many clients that were in jail there for immigration issues.
For human trafficking, or similar immigration issues, possibly. For entering Brazil without going through the proper immigration process or overstaying their VISA, I doubt it very much.
The term "illegal immigrant" does not even officially exist in Brazil. The term officially used is "immigrant in irregular status". The law 7,685 issued in 1988 recognizes that immigration is a human right and set up rules for any illegal immigrant in Brazil to normalize their status. Unless if you cause trouble, like being on a street brawl, or involved with theft, smuggling, gambling or similar, the police will never arrest and deport you for just being there illegally.
Another possibility is the arrest at the immigration checkpoint at the point of entry (like an airport) if the immigration official suspect that you may lack enough funds to stay or if he suspects that you plan to overstay your visa. Then yes, you might be detained and deported (but never face charges). But the rule of thumb is, once you are in, you are in.
That is why a few years ago, for example, the state of Acre had to declare state of emergency, as it got swamped by over 50 thousand illegal (irregular) Haitian immigrants. Once they made it successful across the border from Peru or Bolivia, the policy is that they would not be deported. But the state of Acre, a poor northern state, simply did not have the means to process them, so the federal government had to step in.
None were or will be deported. That is the policy. You make it across the border and don't commit crimes afterwards. You will stay. But hey, don;t take my word for it.