GTCB did produce Mabs for Abbott and Elan in transgenic goats if my memory serves me correctly. I believe these were derived from cell line sources as well. It is not clear why these collaborations were not pursued further. A speculation would be that if a company has a CHO-cell line protein that works they would go with that platform as it is tried and true. This does not mean that it is better just easier for the company to implement with existing facilities and personnel. Also at the time of these collaborations GTCB had no approved product.
If GTCB/Abbott/Elan has such data comparing their goat derived Mabs with the cell line derived product I doubt that it would be made available. The purpose of these companies is not to get pubs in Nature Biotechnology but to produce profit from patented technology to their competitive (i.e. proprietary) advantage.
In addition one of the foci of GTCB is to produce proteins that are difficult to express in cell systems. They may have to compete down the road if another company decides to produce the same protein in a cell line as they are in the goats. However if they choose wisely (and IMO they have) they won't be competing against CHO-cell derived proteins in the near term. There are plenty of targets in the plasma protein arena that require large quantities of material for therapeutic use that cannot be served by cell systems.