It is finally working !!!
I still don't know witch one are the latest , but it works with bluez-zaurus_2.12_2.4.20_alpha4_arm.ipk and the OESF Howto
Here.
I tried several config, have some very strange stuff (Freeze, even a "ghost" that continuously hit the keyboard sometimes, so several reboot) each time i remove the USB BT dongle or while i'm tryinfg to configure the BT connections... But the GPRS connection is working...
First the phone and the Z was able to pair, but the connection stop working after few seconds. I thought that it was link to the bluez drivers, but it was just a wrong Init string
Here is my config
C1000
Sharp Rom
tetsu Kernel,
bluez-zaurus_2.12_2.4.20_alpha4_arm.ipk
qtopia-bluetoothnetworkapplet_1.0.1_arm.ipk
USB BT Dongle : "microtune BT Usb device"
i-river USB host cable
Operator : Orange France
Mobile Phone : S55 Siemens
Bluetooth network applet Config:Name:S55 Orange
User Name and Password: orange
Phone:*99***1#
BT device : /dev/rfcomm0
Init String:AT+cgdcont=1,"IP","orange.fr"
<--the good init string for orange franceSpeed:57600
Hardware ctrl checked
Auto checked on network tab, no proxies