Efforts to take Boston’s skyline spectacularly vertical have snagged in political and business realities. In March, Renzo Piano bowed out of developer Steve Belkin’s controversial plan for an 80-story office tower, which at 1,000 feet would be New England’s tallest. The city had already granted preliminary approval to the project, but preservationists objected that the scheme included demolishing a noted building by Paul Rudolph. The tower’s scale and economic viability have also been questioned.

In a statement announcing his departure, Piano expressed support for what he termed a “challenging adventure.” But sources familiar with the project say that the split was caused by creative differences, primarily over Belkin’s decision to widen the building from 140 feet per side to 160 feet, which Piano thought would ruin the tower’s slim silhouette and deprive the building and surrounding space of light and air.

Following Piano’s exit, Belkin’s Trans National Properties tapped CBT Architects, a Boston-based firm that was working on the project with the Italian architect, to carry his scheme to completion. It also added Ove Arup & Partners and urban designer Ken Greenberg.

“Now that we have a conceptual design for the tower, we are working diligently with our team to implement the vision,” a Trans National spokesperson says. Even so, Piano is said to be unhappy with the degree to which the altered design is being attributed to him.

Belkin’s financial plan for the tower was due to the city in April. Kairos Shen, director of planning for the Boston Redevelopment Authority, says that shuffle of design team members won’t scuttle the project, but it could create complications. “If we don’t think they have the right people involved, the city may recommend changes.”

The project has the backing of Boston’s mayor, Tom Menino, who last year solicited designs for an iconic tower to occupy the site of a city-owned parking garage in the financial district. Trans National was the sole respondent. It owns the Rudolph-designed Blue Cross/Blue Shield Building nearby and proposed to demolish the 1960-vintage structure to create space for a large public plaza. Piano was prepared to save some but not all of the building, according to sources.

The Boston Landmarks commission issued a demolition delay for the Rudolph structure in March. Beyond that, Shen says, “the city will not allow demolition unless there is a signed development agreement and a schedule for actual construction of the new building.”