Workers at Opel, German politicians and customers of Canada's Magna expressed concern on Friday about whether General Motors' decision to sell a majority of Opel to Magna and Russia's Sberbank will turn out to be a favorable deal.

Many of their questions about state aid and possible plant closures remained unanswered, however, and some details are yet to be worked out between the German government, GM and the Magna consortium before the deal's closing, which is expected by the end of November.

GM agreed this week to sell a 55 percent stake of the European carmaker to the consortium, ending months of fraught negotiations that had weighed on Opel and its 50,000 workers.

Two people close to the deal told Reuters on Friday that further details to be worked out concern primarily the German federal and state government's commitments to provide aid for Opel and did not pose a threat to the deal's completion.

Germany has promised 4.5 billion euros ($6.6 billion) in state guarantees, to which other European governments were expected to contribute. But as the dust settled on the Opel deal, it was still unclear when and how much they would give.

We'll make a decision (on the timing) once we have further details, a spokesman for Spain's industry ministry said.

Any aid will require approval by the European Union.

Opel has four plants in Germany that make cars ranging from the three-door Corsa subcompact to Zafira vans, two factories in Britain under the Vauxhall badge, and major sites in Belgium, Poland and Spain.

It was not yet clear on Friday how many of Opel's factories would be shut as part of sweeping restructuring that its new owners hope will return the carmaker to profitability from 2011.

Harald Lieske, head of the works council at the Opel plant in the eastern German city of Eisenach, told Reuters that labor leaders hoped to start talks with the new owners next week.

Magna has said it could close a Belgian plant in Antwerp and a British factory in Luton if failed to lure new contracts that would use their capacity.

CLIENT BACKLASH?

Two weeks ahead of federal elections in Germany, some politicians said they had doubts that all details of the agreement would turn out to be favorable.

Guido Westerwelle, whose Free Democrat (FDP) party could form a coalition with German Chancellor Angela Merkel's party following the elections, said he expected many details of the deal would remain sealed until after the September 27 poll.

This was all about giving the government a chance to report such a success in the media shortly before elections, he told German television station ZDF late on Thursday.

The premier of the German state of Hesse -- home to Opel's main plant -- also warned there was still a lot of work ahead.

Jobs will be cut, in Germany and in Europe. This is not a walk in the park, this is currently a sick company, Roland Koch said on German radio station rbb-Inforadio.

There is also concern now that Magna's customers, which include major carmakers such as Toyota, Ford and BMW, could be unhappy about the Canadian automotive supplier's tie-up with one of their competitors.

Some Magna customers including Volkswagen have already expressed concern about the potential conflict of interest the deal poses.

Magna sought to allay these fears by promising to ringfence its Opel operations once it takes control of the former GM unit.

As soon as the takeover is successfully completed, Magna will erect appropriate firewalls to guarantee a complete separation of its current automotive supplier business and Opel, so that confidential customer information remains completely protected, Magna founder and Chairman Frank Stronach said in a statement.

(Additional reporting by Philipp Halstrick and Angelika Gruber in Frankfurt, Tracy Rucinski in Madrid and Scot Stevenson in Berlin; Editing by Hans Peters)

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