Comcast Corp. held the grand opening of its new half-billion-dollar headquarters in its airy lobby Friday night, without all the state and local tax breaks that Gov. Rendell and landlord Liberty Property Trust once tried to get for it.

Four years earlier, a coalition of rival Center City building owners and out-of-town Republicans had blocked Liberty's attempt to rope Comcast's Center City site into one of the state's Keystone Opportunity Zones.

Properties in those zones are exempt from state and local taxes, including corporate and personal income taxes, sales taxes and financial taxes.

Naysayers in the General Assembly who defeated the Rendell-Liberty-Comcast axis said opportunity zones ought to be limited to rusty industrial sites already on the state's tax-free list, such as the former Philadelphia Navy Yard and U.S. Steel Corp.'s old Fairless Works.

Despite Harrisburg's brush-off, Comcast has brought more than 1,300 new workers to Philadelphia to fill its tower, including some relocated from South Jersey and Connecticut, Liberty and Comcast said in a report Friday by Econsult Corp. of West Philadelphia.

New wage, income and sales taxes from those workers and other new arrivals will more than repay taxpayers for the standard city tax abatements and state job credits and the special $30 million underground SEPTA tunnel that the Comcast building got, even without the additional zone benefits.

Meanwhile, Harrisburg is reviewing plans that would make it easier for future builders to get "zoned" in places such as Center City.

"The Keystone Opportunity Zone has been far and away the most important business tool we have," Michael Rossman, director of Rendell's Governor's Action Team, told me last week.

He listed the companies, from Spain to South Korea, that lately have flooded these zones with hundreds of new manufacturing and energy-industry jobs, and he reminded me of the construction crews transforming the older reaches of the Navy Yard into a hub for big corporate headquarters and little tech firms.

Pennsylvania needs the zones, Rossman said, because New York, New Jersey, Michigan and other big states have their own, and they'll clobber Pennsylvania if it fails to compete.

If Harrisburg fails to pass any new zone legislation, the existing zones and their benefits will expire. Rendell's new budget proposal shows that tax benefits from currently authorized zones are projected to fall from $39 million in 2007 to $35 million this year, to $28 million in 2012, and eventually to zero. And that's not counting the concurrent local tax breaks in the zones, which Harrisburg doesn't track.

The governor's budget proposal and new KOZ legislation, Rossman said, will make it possible to offer more tax breaks. The current Senate version would make it easier to add new KOZs; the House version would make it possible for counties to swap unused zone tax breaks from one property to another, without going through the General Assembly.

There's a surplus of new high-rise-tower proposals circling Center City at the moment, all sadly lacking the kind of corporate tenants who pay for skyline-altering architectural statements.

But the next time an ambitious developer wants Keystone Opportunity Zone tax breaks to sweeten the pot, he might not have to contend with the kind of upstate opposition that made Comcast pay a little more of its own way.