Well what is the precise, distinct problem with them using a private contractor to do this? The contractor is collecting information which is public, and relaying information which may indicate that there is a case that ICE could pursue.

As far as I am aware, ICE already did this form of OSI in-house, but probably less effectively.

> >(A)ICE is also known to be monitoring people sympathetic to enforcing immigrants’ rights, labelling them as “Anti-Trump” protestors.

ICE working with this contractor is not what would cause them to monitor "people sympathetic to enforcing immigrants’ rights"†.

† Also, I think the quoted material is a bit too reductive: although there has been a move away from the phrase "illegal alien" since people have started associating the word with space aliens or something, there remains a pretty clear delineation between immigrants generally, and illegal aliens. I suspect that ICE is interested particularly in monitoring people who are endorsing an unlawful act[0], and likely to be providing material support for such an act. I suspect they are considerably less interested in people who, for example, help lawful resident aliens gain access to legal resources or social support.

[0]: https://www.law.cornell.edu/uscode/text/8/1325