Well, I ran the same sheet (my sheet, exactly the same that fails in Maple 15) in my old copy of Maple 12 and, guess what, it works there!!
I then ran your code in Maple 15, and it fails with the same symptom: nothing below 1E-8 gets plotted. The vector Y gets created correctly, it is the plotting that is fouled up.
So, smells like a bug in Maple 15 & I am pretty sure I run 15.01 at my home (here at work it is Maple 15.00).
What am I to do?? I don't really want to revert to Maple 12 (even though for this particular calculation I could). I consider this a rather serious issue. Is there anyway to get this fixed?? Or is there any hidden parameter that makes logplot ignore values below 1E-8??