By Andy MukherjeeIndia’s 158-year-old Tata Group wants its holding company to stay private. Last week, the Reserve Bank of India retained Tata Sons Pvt. The SP Group, a pedigreed construction and engineering business, can’t sell its Tata Sons shares without the latter’s approval. But Tata Sons’ financial health remains overly dependent on dividends from Tata Consultancy Services Ltd., India’s No. With AI posing serious risks to the outsourcing firm’s future profitability, Tata Sons needs its own access to public equity markets.