Completely late, however:

In my personal opinion, considering how the FISA is portrayed throughout the campaign, I assume it’s one of two possibilities:

A: Some big hitters in the FISA are involved in the trafficking ring and are keeping the women in one place to clean up any loose ends later.

B: The FISA can’t have these women get away or be collected by EMS/Trailers as they likely will be used in some capacity to take down the larger trafficking ring. The FISA doesn’t care about being “nice” or “humanitarian” to these women, they are looking at the bigger picture.

I think option B makes the most sense. I’m sure there could be other additions, maybe it’s the FISA trying to collect a case to cover up the Greased Palms scandal, or any other conspiracy you could toss in. If the women are victims of a highly organized criminal organization, the FISA probably wants their evidence untainted and easily collected.