There is a lot of very good information available from the State of New York regarding government spending. Financial data for each type of government is available for download and review.
The LOSAP expenditure falls under the group heading of Employee Benefits. The specific category is labeled LOSAP/Miscellaneous, and I am unsure what type of expense falls under Miscellaneous. The data for towns is suspect, as many towns that I know sponsor a LOSAP are not reporting a LOSAP expense. This is likely because they group that expense into Fire Protection, so it is not being separately identified. Villages and cities appear to have well populated data, but I also haven't spent a lot of time analyzing it. But villages have many expenses other than fire protection, and I'd have to really dig into the numbers to try and isolate how the LOSAP expenditure compares to the overall cost of fire protection.
So to start I'm going to focus on fire districts, since they only provide fire protection.
There are 397 fire districts that report a LOSAP/Miscellaneous expense. As a percentage of total expenditures, the average is about 11% of total expenditures. The median is about 10%. As a percentage of revenue, the average LOSAP expense is about 10.5%, with the median still around 10%.
So on average, a fire district is spending about 10% to 11% of the total budget on LOSAP. More digging will have to be done to try and get more detailed with these numbers, as we'll need to pull together information from various sources. It would be interesting to see additional breakout of DB vs DC plans, and perhaps by county.