Preparing a file for broadcast with CC

I handle a SD 30min TV weekly program that is now moving to a new station and into a time slot where Closed Captioning (CC) is required (WIN network, Australia). Until now I have been simply supplying a .mov file (H.264) which has been acceptable, but I am now required to deliver an MXF file with CC embedded. Getting into CC is a steep learning curve, and I'm trying to work out the new workflow and software required to achieve it.

Currently, my understanding is, that I will now need to:

1. Output the program in MXF format from FCPx via Compressor's presets. At this stage the file needs to be exactly in the format required by the station, though without the CC. (I am not sure Compressor can provide the precise requirements for PAL Broadcast as requested -- see specs below --, but let's assume it can for the moment);

2. CC will then need to be edited and embedded into the MXF file via a second step. I have a CC text file ready to go (in several formats, including .scc format -- converted via rev.com), and I can import this and add to the file using Compressor or MacCaption. [I am not sure if this can be done in step 1 (above) as I have not been able to get the MXF export feature working in FCPx yet].

[I tried adding the CC to a .mov file (600Mb) in Compressor, and it exported to an MXF file of 6Gb! Is this expected?]

Are there any other / better workflows to recommend? Does anyone know a service that can handle all this at a reasonable price and create the broadcast-ready MXF file? The specs are:

FILE TYPE

MXF or GXF wrapper (GXF preferred)

Mpeg 2

Video format: SD Long GOP 4:2:0 @ 8 - 15 Mbps

VIDEO

16:9 Aspect Ratio

720 x 576

Interlaced

PAL 625 lines

50 field/s

25 frames/s

(Refer to OP36 for further details)

CLOSED CAPTIONS

If programming airs between 06:00 and 24:00 on the WIN channel, it must have Closed Captions.

Embedded – SMPTE436M data track and/or

VBI – Line 21 (See OP47 for details.)

Thanks for any help or tips,