In the WaPo, architect

Roger K. Lewis asks “Are trolley lines more than just a fashionable bit of nostalgia?” and writes “Unlike a bus line, a trolley line is a relatively permanent infrastructure investment. Thus with fixed rails and stations, a trolley line can positively affect real estate values and greatly augment economic activity near the line. Property owners, developers and lenders are more willing to incur the risk of investing in projects near a trolley line than in projects near a bus stop.”

OK, I hear this argument all the time. Are we forgetting something (from the history of the Twin Cities streetcar system (see Xie and Levinson (2010) How Streetcars Shaped Suburbia Journal of Economic Geography 10(3), pp. 453-470. for a statistical analysis):

Streetcars are not permanent. Roads are pretty close to permanent. Subways are pretty close to permanent. Streetcars disappeared from almost all US cities (in Lewis’s lifetime).
Second, Bus Rapid Transit (BRT) can achieve the same effect. Of course BRT is more expensive than a bus stop, and provides better service than buses in mixed traffic, but it is also generally less expensive than trolleys, and a lot more flexible as it can serve in neighborhoods. The evidence from the Twin Cities is that while streetcars disappeared, transit service did not. It is not the technology which is permanent, it is the service. If the demand is there, the service will come; if it is not, the service will leave.
See e.g.

Rodriguez, D. A., Targa, F. “Value of Accessibility to Bogotá’s Bus Rapid Transit System,” Transport Reviews, Vol. 24, Number 5, pp. 587-610, 2004. ; and

Ramon Munoz-Raskin, “Walking accessibility to bus rapid transit: Does it affect property values? The case of Bogotá , Colombia“, Transport Policy ,Journal of the Transport Conference on Transport Research Society, Volume 17 (March 2010), pp. 72-84,

Cervero, Robert and Chang Deok Kang (2010) Bus rapid transit impacts on land uses and land values in Seoul, Korea

Perk, Victoria and Martin Catala (2009)Land Use Impacts of Bus Rapid Transit: Effects of BRT Station Proximity on Property Values along the Pittsburgh Martin Luther King, Jr. East Busway

and a dedicated issue of the Journal of Public Transportation

(Lewis article Via Greater Greater Washington .)