I don't get the impression from the description that it will extend its range that far. Instead, it appears it allows reception in what would otherwise be a dead spot in a specific location in its designated market, because of interference. But again, that's just my impression. I welcome those with more technical knowledge to elaborate.  

This appears to be a variation on the synchronous FM repeater theme, with the key words being "close to the ground" and "cellular". This implies a multiplicity of transmitters, each of which will require a separate technical brief and license. 
The CRTC's policy on synchronous rebroadcast transmitters in competitive markets appears to be that they must be within the originating station's 0.5 mV/m contour, and not extend beyond the boundary of the existing 0.5 mV/m contour. See prior decision 2016-305 in which a power increase for CJKX-FM-2 was denied.
 "In Broadcasting Decision 2006-107, the Commission approved the rebroadcasting transmitter CJKX-FM-2 Toronto for the purpose of correcting interference within CJKX-FM's existing 0.5 mV/m service contour and to allow CJKX-FM's listeners who commute to downtown Toronto to receive the station. The establishment of CJKX-FM-2 Toronto was to correct a technical issue and not to expand the primary market of the station. Therefore, although CJKX-FM provides coverage to a portion of the Toronto market, its primary market does not include Toronto. "

Radio.Intern wrote:

markow202 wrote:

So I'll be able to listen to 97.3 clearly at the cottage in Muskoka?  Very confusing when you can stream stations. 

I assume this technology will come in handy more for 93.5 than 97.3.

You turned out to be right on the money, apparently. A few highlights from Stingray's application to the CRTC to "Maxxcast" its station at 93.5 to North York and Mississauga. (I can't link to it directly, since it's in a .pdf file embedded within another file.)

"CFXJ FM has experienced significant signal degradation over the past few years in the Toronto area as new high-rise development and population density has increased. Audiences further from the downtown core – where the CFXJ FM transmitter site is located – frequently have difficulty receiving the station as expected within its authorized parameters.

Should this application be approved, Stingray projects adding two more MaxxCasting SFN (Single Frequency Networking) repeaters in the Greater Toronto Area in the next year – improving signal strength within its authorized contours to all listeners across the GTA.

Approval of this unique application will allow CFXJ FM to enhance its signal within the station’s authorized technical parameters. Audiences will discern a notable difference in signal reliability and overall quality when tuning from home or in vehicles, without the need to change frequencies from 93.5 FM.

The CFXJ FM signal is currently unreliable outside of Toronto’s downtown core, alienating commuter listeners living in North York and Mississauga.

The most obvious fix would be to increase power to the main transmitter at First Canadian Place in downtown Toronto. However, there are technical issues which prohibit such a move.

CFXJ FM 93.5 is first or second adjacent to multiple radio stations in southern Ontario and western New York. CFXJ FM is at maximum output without interfering with these stations. Therefore, a power increase for the main transmitter is impossible.

A search for a new frequency revealed a crowded spectrum in southern Ontario, with no available drop-in signals that would improve coverage for CFXJ FM in the North York and Mississauga regions."

Stingray is proposing to utilize MaxxCasting to drop in concurrent repeater signals in North York and Mississauga on the same 93.5 FM frequency. There will be no additional burden on the frequency spectrum of southern Ontario, nor will first and second adjacent signals be affected outside of the currently authorized parameters of CFXJ FM."

This was back in 2022. Did any of this ever happen? Is it still in the works? And if it did, was it successful?

You can bet if Stingray becomes the first to do this in Canada, they almost certainly will not be the last. 

Move Boom to 93five and have a good look at the numbers. Ratings for boom will remain unchanged.
The signal is not the problem. The format is. 
They can get better ratings out of a Variety Country format on 93.5. 
I'm pretty sure that's a fact.

markow202 wrote:

Radiowiz wrote:

Move Boom to 93five and have a good look at the numbers. Ratings for boom will remain unchanged.
The signal is not the problem. The format is. 
They can get better ratings out of a Variety Country format on 93.5. 
I'm pretty sure that's a fact.

Boom has a way better signal at 97.3 and its working well for them so I wouldnt change that 

I don't think he's suggesting actually doing that, but theoretically illustrating that 93.5's biggest problem isn't its signal.