Remember something that we here in the NYC area might not be aware of - there are national standards for fire company coverage. Engine companies should have a first due area of 3/4 miles in each direction, while truck co's areas are doubled to about 1 1/2 miles. But there are also other requirement - the need to put a first alarm assignment on the scene in about 8 minutes.
Also think that some fire stations go back to the days of horses. There are a lot to take into consideration about placing a fire house. Look at Manhattan's East side -
Eng 21 - 40th btw 2 & 3 Aves
Eng 65 43th West of 5 Ave
Eng 8 51st East of 3 Ave
Eng 23 58th West of 7 Ave
Eng 39 67th West of 3 Ave
Eng 44 75th East of 3 Ave
Eng 22 85th West of 3 Ave
Eng 53 Third Ave @ 102 St
Eng 91 111th West of 2 Ave
Look the list over - the stations in most places are about 10 blocks apart - specially in the area of Central Park. Where the gap increases is in the northern end, 85 ST to 102 St. But remember that when there was an increase of fires in this area, years ago, Eng 89 & Lad 39 were created in the area of 95 St to help protect the area.
At the lower end of this area Eng 65 & 23 can respond to protect both sides of Manhattan with out too much of a delay, but forget holiday periods.
Its hard getting fire companies to cross Central Park with Manhattan's traffic so in most cases East side companies will cover the first alarm responses on there side of the park. Opposite park companies
will respond either 4th due on the first or on the second alarm.