Hi Martin,
What Andreas said.
I run sane from cmd files, been a while since I've used tame as I find it quicker just to type epson1240(.cmd) from the commandline.
Important for sane to know where its backend files are (config files) which in my case are in \apps\sane\conf, this is done with a set command.
set sane_config_dir=\apps\sane\conf (or as you have done, in x:\etc\sane.d)
Then I run scanimage telling it which backend configuration file to use, with the parameters I want.
SCANIMAGE.EXE -d epson2 -l 0 -t 0 -x 215 -y 297 --mode Color --resolution 300 --depth 14 --format=tiff
Tame hides all this from you as its the nice front end gui.
Looking at your results from scanimage -L, "USB scanner (vendor=0x04b8, product=0x1135) at libusb:001:004".
I cant find the vendor ID in any of the conf files (looking at the mine and BWW's), neither can scanimage -L otherwise it would normally indicate more than the the numbers.