If they are not recommended for magnetic ballasts, I would not use them in one.
I do have to say that over the years, I have purchased many different brands of HPS bulbs and I have never found any difference in growth or quality from expensive bulbs versus inexpensive bulbs. I like to change my bulbs out every 6-8 months or so and have taken to just buying the less expensive bulbs. This is another area where I believe there is exaggerated sales hype--I really do not know that any bulb is significantly superior to another, although I do look for bulbs with higher lumens.