CHICAGO (CBS) — Chicagoans trying to plan their activities around the upcoming NATO summit are apparently going to have to wait awhile.

It’s all up to the U.S. Secret Service, which this week conducted a desktop security exercise with more than a dozen local agencies. Right now, everyone appears to be on the same page on everything — except mass transit.

The host committee website tells you about the city’s hopes and dreams for the NATO summit and why it’s such a good thing for Chicago.

LISTEN: WBBM Newsradio’s Bob Roberts Reports

For the potential pitfalls and problems, you have to look elsewhere.

Case in point: the South Shore commuter line. Its trains run on tracks underneath McCormick Place, where NATO delegates will gather Sunday May 20 and Monday May 21.

The Secret Service, CBS 2 has learned, wants to stop all train traffic there for two days. Metra is apparently fighting a Monday shutdown because of the difficulty in busing thousands of commuters around the security zone.

That security zone around McCormick Place will be determined by the Secret Service.

But sources tell CBS 2 Chief Correspondent Jay Levine it’s not expected to disclose what its boundaries will be until about May 1.

South Loop residents could suffer from temporary street closings. But the buildings where those residents live are not expected to be within the security zone because that would make the Secret Service responsible for added patrols.

CTA President Forrest Claypool said the wait for concrete information has been frustrating.

“They don’t give you a lot of notice,” he said.

CTA buses may be used to shuttle riders between the ‘L’ and any temporary Metra Electric and South Shore Line terminal, if rail lines that operate beneath the NATO McCormick Place meeting site are shut down.

CTA Safety director Araceli De La Cruz also said Friday that buses may be needed to deploy police officers to protest sites.  Claypool and Metra Executive Director Alex Clifford said for planners, it has been a daily dose of “what if” scenarios.

“Our planners, as in any case where you any potential impact to Metra service, will always plan appropriately for contingencies,” he said.

Both men say they have asked the Secret Service to give them something concrete before the end of the month.

Also not clear is whether the protest site near McCormick Place, approved by the city, will have to be changed.

Motorcades will be an issue for both residents and commuters. The Illinois State Police reportedly will escort motorcades for up to 70 heads of state who will be traveling to and from McCormick place.

Intelligence experts have been monitoring communications channels of known terrorist groups for potential threats. There has been no “chatter” about targets or tactics.

Authorities also believe the actual number of protestors will be less than what was expected for the now-relocated G-8 Summit.

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