Terantious,

This may not be the easiest way, but I usually pull up the most current line awards (same place you pull up the bid packets online) and scroll down until I start seeing reserve lines. I then take a look at what people were bidding just above that, keeping in mind some people may have actually bid reserve. Then, you settle on a specific line as being the cutoff and count down until you find your line. When the next bid packet comes out, I then look at the difference in block hours from the previous month, as well as how many positions I moved up to determine my chances of getting a line for that month. Someone may have a better way, but this method was pretty accurate.
You might also consider that this company likes 25-30% of the pilots in each domicile to be on reserve. Ftrpilot may have a more precise number, but you can see whether you fall into that percentage of people as well. Hope this helps!

ComairFO