It’s a scenario worthy of a vampire movie. A company once considered dead is still alive. Lehman Brothers, the first domino in a chain of events that brought the economy to its knees four years ago, remains an operating company as a cadre of about 340 staffers toil to sell off the investment bank’s holdings to satisfy creditors. Its real estate portfolio alone is worth $10 billion. Yet employees function in a much less ostentatious environment than other Wall Streeters. Last year’s holiday party was a distinctly low-key affair. By 2017, the bank is expected to be gone for good.