I am looking at your RAW and you won't be able to get much with that. I see very little if any IR effect. My normal settings with the filter were ISO 200, f/7.1-f/8 and 25-30 seconds. You should see some obvious IR effect in the trees. Was there a lot of direct sunlight when you shot this? Do you have another lens you could try?
This is how mine look coming out of the camera:
A700, 16-80 Zeiss, R72 filter, f/5.6, 30s exp, ISO200
I took a quick crack at it with IDC (click photos for full size):
WB off the brightest tree, +1Ev, +60 Contrast, stretched the histogram to fill the range:
WB off the brightest tree, +1Ev, +45 Contrast, -100 Sat (B&W), stretched the histogram to fill the range: