The jobs plan doesn't even have enough Democratic support to pass the Senate, so the likelihood of it making it through both houses is nil. It's more of a political plan than an economic one.
I also think that we have limited capability to make expedient investments in infrastructure with a positive ROI. Take a look at the Columbia River Crossing project between Oregon and Washington states - six years after project inception, the final environmental impact study still hasn't been released. Construction would start in 2013 at the earliest and is estimated to take 5-7 years. Time lines like that are common with large infrastructure projects in the US.