Is it likely that intergalactic stars would still retain their planets?
While near encounters with supermassive black holes are bad for the stability of solar systems [citation needed?], many intergalactic stars become intergalactic without a close encounter. They are part of streams and tidal tails that emerge when galaxies or globular clusters get tidally disrupted by another galaxy. 

Still, even while encounters with black holes are usually disruptive simulations suggest that some planets may remain around the star. This is most likely for planets real close to the star, like hot jupiters.