Ann: Third Supplementary Target's Statement to Iberdrola Offer, page-5

they become a substantial shareholder as they have removed all conditions now.... IFN board remain in control

Seeing it appears TCI have now sold out - I would assume it would be a replacement of the board position held by them with a member from Iberdola... but if they get close to 50% I could hazard they may ask for more than one seat.

realistically - management and board need to be refreshed after this deal if the TO doesn't reach 50.1%... as it showed they thought they were out of options to grow further themselves.