more info on mpeg4 in MPEG2-TS 
http://webb.ens-cachan.fr/ftp/mirror/MPlayer/doc-tech/ISO-13818-Amd7.pdf

you need the latest verion from cvs, see bug #150449
get it send from vlc[1]
to play it right away:
gst-launch-0.8 -v udpsrc port=1234  ! ffdemux_mpegts ! ffdec_mpeg4 ! xvimagesink
to save to file first:
gst-launch-0.8 -v udpsrc port=1234  ! filesink location=/tmp/streamdump.ts
and play later:
gst-launch-0.8 -v filesrc location=/tmp/streamdump.ts ! ffdemux_mpegts !
ffdec_mpeg4 ! xvimagesink

switching on debuging in gst-ffmpeg/gst-libs/ext/ffmpeg/libavformat/mpegts.c
you get:

gst-launch-0.8 -v filesrc location=/tmp/streamdump.ts ! ffdemux_mpegts !
ffdec_mpeg4 ! xvimagesink
RUNNING pipeline ...
/pipeline0/filesrc0.src: caps = video/mpegts, systemstream=(boolean)true
/pipeline0/ffdemux_mpegts0.sink: caps = video/mpegts, systemstream=(boolean)true
/pipeline0/filesrc0.src: active = TRUE
/pipeline0/ffdemux_mpegts0.sink: active = TRUE
Filter: pid=0x11
Filter: pid=0x0
PAT:
00000000  00 b0 0d 00 01 e9 00 00 00 01 e0 42 bc f9 5d 71 ...........B..]q
sid=0x1 pid=0x42
new_service: sid=0x0001 provider='' name='Service 1
'
tuning to 'Service 1
'
Filter: pid=0x0
PAT:
00000000  00 b0 0d 00 01 e9 00 00 00 01 e0 42 bc f9 5d 71 ...........B..]q
sid=0x1 pid=0x42
Filter: pid=0x42
PMT:
00000000  02 b0 7e 00 01 f7 00 00 e0 44 f0 68 1d 66 01 02 ..~......D.h.f..
00000010  80 80 61 00 4f ff ff fe fe ff 03 80 80 56 00 44 ..a.O........V.D
00000020  1f 04 80 80 43 20 11 10 00 00 7f ff ff ff 00 00 ....C ..........
00000030  00 00 05 80 80 32 00 00 01 b0 01 00 00 01 b5 89 .....2..........
00000040  13 00 00 01 00 00 00 01 20 00 c4 8d 88 00 cd 0c ........ .......
00000050  04 24 14 63 00 00 01 b2 46 46 6d 70 65 67 30 2e .$.c....FFmpeg0.
00000060  34 2e 38 62 34 37 31 34 06 80 80 08 01 00 00 00 4.8b4714........
00000070  00 00 00 00 10 e0 44 f0 04 1f 02 00 44 81 23 a7 ......D.....D.#.
00000080  76                                              v
sid=0x1 sec_num=0/0
pcr_pid=0x44
stream_type=16 pid=0x44
tuning done
/pipeline0/filesrc0.src: active = FALSE
/pipeline0/ffdemux_mpegts0.sink: active = FALSE
Execution ended after 1 iterations (sum 104077000 ns, average 104077000 ns, min
104077000 ns, max 104077000 ns).
/pipeline0/filesrc0.src: caps = NULL
/pipeline0/ffdemux_mpegts0.sink: caps = NULL


[1]
vlc clip.avi --no-audio --sout
'#transcode{size=320x240,vcodec=mp4v,vb=1200,vt=800000,keyint=80,deinterlace,hq}:std{access=udp,mux=ts,url=127.0.0.1}'
--ttl 4