Here is an Android 4.2.2 Jelly Bean rooted firmware for the new PIPO M7T tablet (aka Max-M7T / DS892B) offering 3G & phone call features. This firmware is based on latest PiPO update dated 2014/01/21. 

( 20140121_DS892B_M7T_3G_4.2_通话_威广骏TP_#633.rar )

Build information:

Kernel: Linux version 3.0.36+ (cdy@mid-server) (gcc version 4.4.3 (GCC) ) #633 SMP PREEMPT Tue Jan 21 16:08:28 CST 2014

Android 4.2.2 JB: rk30sdk/rk30sdk/rk30sdk:4.2.2/JDQ39/eng.ljh.20140120.104625:eng/opinions-on-teclast-p90hdst-keys

ro.rksdk.version=RK30_ANDROID4.2.2-SDK-v1.00.00

Custom firmware features:

• root with latest SuperSU version 1.93 (free version)
• removed most Chinese and unnecessary applications
• Google Play Store fixes so more application are visible/compatible
• updated busybox v1.21.0.git (2012-11-29)
• Unix like init.d boot scripts support, more details on init.d scripts here
• changed permissions on external sdcard to allow write access
• increased space for applications (/data partition) to 4 GB
• disabled OTA updates (may cause problems, see Notes below)
• kernel modules (cifs, tun, lan, serial, xpad) compiled by Oma & Crew RKTablets, thank guys!
• NEW! : optional ClockworkMod (CWM) Recovery easy install package

Notes: 

- any update received thru OTA may interfere with our custom firmware, we recommend not to apply any OTA update

Download: kasty-pipo-m7t-422-20140121-rooted4.zip

Flash with Rockchip Batch Tool version 1.7, use Restore button.

Please report any problem with this firmware, I can't verify this custom firmware works as I don't have a PIPO M7T tablet to test the custom firmware.