Not sure how relevant it is.. but under linux (ubuntu something)

umount /dev/usbstoragedevice

unmounts the file system.. but you could always mount it again

mount /dev/usbstoragedevice /mnt/usbstick

Ejecting is something different

eject /dev/usbstoragedevice
Now the device is unmounted and is no longer accessible..

eject is traditionally used with cdrom drives.. to open the tray..

eject -t closes the tray and although we're talking USB memory sticks

eject -t /dev/usbstoragedevice

is effectively the same as plugging the USB device back in..the OS detects it as a attach and will according to what does normally mount the device again..

So

ejecting the N900 from the host should effectively be the same as a USB disconnect without removing the cable.. If I had my linux machine with me, I'd give it a go..