There is a reason why the new addition to the Chateau Laurier Hotel in Ottawa looks completely different.

Two completely different businesses will inhabit the same plot of land in downtown Ottawa.
"How does a hotel developer compete with a residential developer for the same plot of land?" was the title of a presentation that Peter Clewes of architectsAlliance attended; at the Canadian Hotel Investment Conference, May 13 and 14, 2019, Toronto.
Strata Title Property
Strata title allows individual ownership of part of a property (called a lot and generally an apartment or townhouse) combined with shared ownership in the remainder (called 'Common Property' e.g. foyers, driveway, garden) through a legal entity called the owners corporation or body corporation. (From: Wikipedia.)
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Strata Hotels and Motels - BC Assessment Page 4/11
These properties are hotels that have been stratified for individual unit ownership. These hotels are managed by a management company and are governed by an elected Strata council representing the owners of the property. Each unit may be sold independently with the rental/owner use unique to each hotel.
Strata hotels, otherwise known as condo hotels, are hotel properties where investors can purchase individual units of the hotel itself.

The City of Ottawa KNOWS that the Chateau Laurier extension is really a separate condominium development:
Waste Collection
Separate collection areas will be required for the commercial (hotel) and residential units. (From: "Chateau Laurier Expansion, 1 Rideau Street Ottawa, Ontario-Page 13 of 94-City of Ottawa Planner, Development Review, Planning and Growth Management.)
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A traffic impact study has not been conducted to find out how Mackenze Avenue will be affected by the condo project:
     "75 vph-150 vph requires a Transportation Brief; greater than 150 vph requires a Transportation Impact Study." (From: Chateau Laurier Expansion, 1 Rideau Street Ottawa, Ontario-Page 13 of 94.)

Views of the Hotel du Canada are not legally protected:
Heritage Comments

• While there are no legally protected views of the Chateau Laurier, there are several iconic views that contribute to the Chateau's heritage value as a landmark building. These views are well documented in the NCC's 2008 "Chateau Laurier Urban Design Guidance" documents and impacts on these views should be assessed through the design process.

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There is a reason why the National Capital Commission will never try to save the Chateau Laurier---the federal Crown corporation is encouraging the redevelopment and commercialization of property on the northern side of the landmark:
Municipal Regulations 
Expansion of the Chateau Laurier is controlled by the City of Ottawa's Central Area Official Plan, Zoning bylaws and heritage overlay, which together permit-

• Hotel, housing, office, restaurant and retail uses. (From: 15/31 - "Chateau Laurier Urban Design Guidance."( National Capital Commission, 2008)

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The National Capital Commission does not respect the will of the people, which can be documented by the following examples---

1.)  A new Civic Hospital will be constructed on the grounds of the Experimental Farm despite overwhelming opposition--
-Friends of the Farm;
- Friends of the Central Experimental Farm;
- Protect the Farm-Home|Facebook;
- Saving the Central Experimental Farm-Heritage Ottawa;
- COALITION TO SAVE THE CENTRAL EXPERIMENTAL FARM;
- Canadian Council of Food Sovereignty and Health;
- Save the Central Experimental Farm - Greenspace Alliance of Canada's Capital;
- Coalition to Protect the Central Experimental Farm National Historic Site of Canada;
- The National Trust for Canada;
- Save the Farm - Protest to save our trees and green space - Ecology Ottawa - see the YouTube video "Ottawa prepares to hand over historic farm land to corporate developers."

2.)  The Dominion Astrophysical Observatory and the adjacent buildings may be demolished.

3.)  Moffat Farm was sold to a developer who built a subdivision called "Prince of Wales on the Rideau" near Mooney's Bay. There was intense lobbying to try to save the 88-acre Veterans Affairs federal property.

4.)  The Daly Building land was funnelled to a condominium builder.

5.)  According to an NCC, City of Ottawa and Parks Canada commissioned document called "Animating the Rideau Canal" the UNESCO World Heritage Site and adjacent lands are facing enormous changes.

6.)  The NCC is not protecting a federal park in Little Italy called "Queen Juliana Park", see the petitions including "Stop the rezoning of Queen Juliana Park at 870 Carling Avenue".

7.)  Agriculture Canada shut down the Greenbelt Research Farm and the thousands of acres of land were automatically transferred to the NCC.