Three key public-safety organizations today filed a joint letter with the FCC indicating that they would agree with a portion of Sprint Nextel’s proposal to vacate its interleaved channels in the 800 MHz band in stages, providing the carrier with much-needed spectral-capacity relief for its iDEN network as rebanding proceeds.

In its letter, the Association of Public-Safety Communications Officials (APCO), the International Association of Chiefs of Police (IACP) and the International Association of Fire Chiefs (IAFC) stated that Sprint Nextel’s proposal to clear its interleaved channels in stages—where interleaved clearance would be reciprocated by public-safety agencies clearing their channels for the carrier—is “not unreasonable, and we would not object to its adoption.”

But the public-safety entities included a notable caveat in their support for the Sprint Nextel plan: that the carrier vacate all of its interleaved channels within 60 days of a public-safety agency being prepared to operate on the spectrum after July 1, 2009. This “firm date” coincides with the date the FCC recently gave hundreds of public agencies as the extended target date to complete rebanding.

FCC rules called for Sprint Nextel to vacate its interleaved channels on Thursday, which was the FCC’s original completion date for 800 MHz rebanding. While a federal appeals court this spring upheld the FCC deadline, Sprint Nextel last week offered its proposal, and the FCC granted a 30-day extension so it could consider the matter.

Under the Sprint Nextel proposal, the carrier would clear 20 channels in its interleaved spectrum immediately, then clear 40 more channels in a region when 25% of the NPSPAC licensees have rebanded and clear another 60 channels when 50% of the NPSPAC licensees have rebanded. Sprint Nextel would vacate an additional 80 channels when 75% and 90% thresholds are reached, and the carrier would clear all interleaved channels after all NPSPAC licensees have completed the rebanding process.

Interleaved channels cleared by Sprint Nextel would represent new spectrum to public-safety agencies, which has a “pent-up demand” for additional capacity, according the public-safety letter to the FCC. The FCC has not yet established a process for public-safety entities to apply for licenses to this spectrum.

Once such procedures have been established, public-safety entities are in a position to begin using the channels relatively soon after securing a license for the spectrum, said Robert Gurss, APCO’s director of legal and government affairs.

“I think a lot of the use is going to be existing 800 MHz licensees who already have the equipment and probably just need to make a minor adjustment to their equipment to use the additional channels,” Gurss said during an interview with MRT. “So, while it could be a new system, most of the early users are going to be expansions of existing systems.”

While challenging the FCC’s June 26 deadline for vacating the interleaved channels in court, Sprint Nextel contended that clearing that spectrum would “cripple” its iDEN network in many areas. In an SEC filing earlier this year, the carrier estimated that having to vacate the interleaved channels next week would have a negative impact that likely would be “material” amount, which some analysts have estimated to be between $1 billion and $2.8 billion.