Some about the 2010 gas explosion here
It's still the subject of litigation it seems. Apparently the company that ran the line had been doing upkeep work on other stretches locally, fairly near the portion of pipeline that blew open, though not on that precise stretch. Also, federal investigators found that the very portion that cracked had showed several dodgy welding seams, which might
have come from still earlier repairs, though they didn't necessarily have to be of such origin.
San Bruno Police declared the area a crime scene to determine if foul play was involved. The National Transportation Safety Board began an investigation into the cause of the explosion. During the days prior to the explosion, some residents reported smelling natural gas in the area. A source within PG&E reported a break in natural gas line number 132 caused the explosion. The gas line is a large 30-inch (76 cm) steel pipe. National Transportation Safety Board vice chairman Christopher Hart said at a briefing that the segment of pipe that blew out onto the street was 28 feet (8.5 m) long, the explosion sent that piece of pipe about 100 feet (30 m) and the blast created a crater 167 feet (51 m) long and 26 feet (7.9 m) wide. He said that an inspection of the severed pipe chunk revealed that it was made of several smaller sections that had been welded together and that a seam ran its length. The presence of the welds did not necessarily indicate the pipe had been repaired, he said. Newer pipelines are usually manufactured into the shape needed for these applications, rather than having multiple weaker welded sections that could potentially leak or break.
In January 2011, federal investigators reported that they found numerous defective welds in the pipeline. The thickness of the pipe varied, and some welds did not penetrate the pipes completely. As PG&E increased the pressure in the pipes to meet growing energy demand, the defective welds were further weakened until their failure. As the pipeline was installed in 1956, modern testing methods such as X-rays were not available to detect the problem at that time.
So it was an old line, laid out the 1950s, and both wear on the pipe itself and shoddy upkeep work may have contributed to the blast. It looks like Pacific Gas were not very good at keeping proper logs of their upkeep and quality checks either - it says earlier in the WP article that "PG&E was unable to provide documentation for details of some of its gas transmission pipelines" - referrring to this article in The Examiner
It's impossible to say how much gas the NYC pipe would actually carry in time, of course, but seeing that it's the New York area with huge potential demand and a pipe of the same width as the Bay area one, the parallel between them seems kind of justified. Just adding in some material here.