Yes you can teamkill but I wouldn't suggest doing that in a mission unless you want to loose.
APB Minimum system requirementsREQUIRED: Internet Connection of 256kbits/sec
PC OS: Windows XP, Windows Vista, Windows 7
CPU: 2.13GHz Core Duo 2, Dual Core
RAM: 2GB RAM
HARD DRIVE: 15 GB
DVD-ROM: 8x Speed
VIDEO CARD: 7800 with 256Mb and support for Pixel Shader 3.0, or ATI equivalent
SOUND CARD: DirectX compatible
DIRECTX: 9.0c
INPUT: Keyboard, Mouse, Headset with microphone required for Voice chat
APB Recommended System RequirementsCPU: 2.4GHz Core Duo 2, quad-core,
RAM: 4GB RAM
VIDEO CARD: GeForce 8800GT with 512MB or ATI equivalent.
Broadband Connection recommended.
APB uses the UT3 engine, so you can try out Unreal Tournament 3, see if you can run it, if you can run UT3 imagine APB being a little heavier. If you can't then you will have to wait for Gamerfirst to bring out a client for people with crappy pc's
or upgrade your PC