The questions is whether this is a case of General Motors planning for a future model or protecting an existing mark, the name "Electra." The name hasn't been used since 1990, when the final Buick model dropped the name, though it was used for over 30 years prior.
There's a very good hint at the intent of the trademark, in the trademark filing itself: the filing basis. The trademark search result lists the application as filed under basis 1B, meaning filed under the requirements of section 1(b) of Chapter 37 of the Code of Federal Regulations, Part 2. This basis requires "a bona fide intent to use the mark in connection with the goods or services listed in the application."
General Motors' U.S. PTO trademark search result for Electra
So there you have it, government-filed proof that General Motors has registered its intent to use the Electra trademark as of June 5, 2012. What, exactly that means for Buick, or what the car itself may be, remains up in the air.