I would definately bring my own medication with me for an asthma attack. There is nothing worse than not being able to breathe. I don't know if they can do a breathing treatment. I would imagine so but you never know. When on the Horizon last year I had quite a few small attacks ( don't know why) but my own medication worked just fine. Good luck
Definitely take your own. I accidently packed my ventolin and atrovent for my nebuliser on the last night. I went down to the medical area and they did have the two drugs at $4 each, but then $50 for the doctor to write the prescription.
I now have a home pack with all my tabs and nebs in and leave it in my carry on, so it doesn't get packed away accidently again (you learn by your mistakes).