Teleworker phones don't use Port 69 for TFTP. I don't have my notes available, maybe someone else will chime in.
It is Port 20001/UDP
The proper port forwarding for remote phones is (from memory, so forgive if I'm wrong):
69, 20001/UDP - TFTP (69 is attemped first, 20001 is the fallback... most routers do not port forward 69/UDP well)
6800-6802/TCP - Applications
3998 and 3999/TCP - Keys (SAC)
50098-50508/UDP - RTP from set to 5000
6004-6261/UDP - RTP to set from 5000
The weird part here is the phones don't need TFTP, they will just timeout and continue to boot and generally work (unless you have one that was on a 3300 and trying to register to a 5000 or vis-versa)