Right now, --temp-build is only issued for the short syntax dub file.d, but dub --single file.d should build in the current directory. Did you test with the latest beta/master?

I tested it with the windows zip version 1.0.0 from http://code.dlang.org/download. This version builds the executable in a temp folder. I will try the latest git sources and will let you know the result.
Kind regards