Basically, the only case possible is if Texas authorities made a threat, or forced the migrants to board the buses.
If they were just told of better work-conditions in NYC, given a bus ticket and a box-lunch, with a dozen beers to drink during the 24 hour 'journey'....there's just not a legal case that you can make out of this.
It would be like those Vegas casinos offering you in Tucson a free bus ticket (with a bag of snacks)....to journey for six hours to reach a casino....gamble for six hours, and then journey back home.
Hate crime? No.
If the Texas guy said there's better paying jobs in NYC? Well....there is, and no one can argue about that in a court.
The idea here by the Biden administration that you'd just let folks cross, and then maybe use some weird set-up to take some to special sites in Florida, or various Republican strongholds? Well....the Republican states figured this out and 'played' another hand of poker.
What'll happen? I suspect by December....some House draft bill will say that you can't charter buses or planes for crossing state lines, unless you get permission from the destination-state to accept the folks. But in doing so.....you will make state-to-state tourism nearly impossible to function.
It is truly screwed-up but no one wanted a true border.