Not that anyone will be surprised, but Tata (nor any winning bidder, if not Tata) can't simply send Ford a money order for $2 billion and have Jaguar and Land Rover delivered to its door. Jaguar and Land Rover are so tied up with Ford that "the buyer of the brands would ... need Ford's research facilities to upgrade the products." And Ford won't give that access away for free. Tata will also be assuming pension liabilities, and though there hasn't been a number put to it, we all know how expensive that can get.
The result is that Tata and Ford are not discussing one deal, but 15-20 deals. All Ford would say is that they "are in substantive and detailed discussions with a view to securing an agreement." The deals would ostensibly secure continuation of parts like engines and technology, support for those parts, and the undoubtedly intense and lengthy training that Tata would need to insure the smoothest transition possible. All of which shows that this sale has not only gotten much more expensive, but much more complex, and for a much longer time to come.