I have that happen a lot with semi's. though not because the driver wants to get into a right turn lane. But because they are passing me & are coming back over. Sometimes it is because there is an oncoming vehicle & the driver thinks he is far enough past me. When a semi. passes I slow down & make sure I fall behind them so when they do come over to early there is no chance of collision.

It is a scarier feeling compared to when a car does it.