I have a 250w MV lamp I would like to use in a fixture but I don't have a 250w MV ballast. I was thinking about using one of my spare 150w or 250w HPS ballast without an ignitor to run the 250w MV lamp but have 2 questions.
The first question is weather the HPS ballasts can run the MV lamp without it overdrawing power and exploding or if it won't fully warm up.
The second question is if it can be done, is it safe?

The 250W HPS ballast (about 3.1A nominal, with the higher arc voltage it will be somewhere around 2.9A) would overload the MV lamp (about 2.1A nominal), the 150W HPS ballast (1.8A nominal) will underdrive it (with the 130V arc it will feedr about 1.6A or so). The underdriving on the 150W ballast would mean lower lamp performance (efficacy, so light output), but otherwise it should be OK. The wear rate I would expect the same as on the rated ballast, because the lamp wear comes mainly from the start cycles.
You may measure the current the 150W HPS ballast feed and maybe add a smaller fluorescent ballast (with the 130V arc the PL-S adds about 0.15A, F15T8 adds about 0.18A, single lamp F18T8 adds about 0.3A) in parallel to reach the rated 2.15A. But better be slightly below the rated current than above.

There are two AEG Koffer 150 near Neve-Hen neighborhood, Kiryat Ata, with 250W MV lamps working on their HPS gear. They overburning like hell.