The way it works with Rabbanut mehadrin, they can carry different hechsherim for the meat, chicken, vegetables, etc. So if they clearly said that the meat is Badatz beis yosef, don't eat it. It is also very helpful to try to figure out in rabbanut mehadrin restaurants if the mashgiach is a yirei shamayim doing his job well. Although rabbanut standards are high, the rabbanut is not on top of things, and it usually comes down to the reliability of the mashgiach.