Some other links for ICE, Euronext, and Eurex futures SPAN margins. Certainly not all-inclusive, but it's a start:
ICE Europe Energy Spread Margin Rates:
https://www.theice.com/ClearEuropeSpanParameterFiles.shtml
Liffe Euronext Equity Index Spread Margin Rates:
https://globalderivatives.nyx.com/sites/globalderivatives.nyx.com/files/index_margins_03172014.pdf
Eurex Spread Margin Parameters:
http://www.eurexchange.com/exchange-en/market-data/clearing-data/risk-parameters/
ICE Europe Energy Spread Margin Rates:
https://www.theice.com/ClearEuropeSpanParameterFiles.shtml
Liffe Euronext Equity Index Spread Margin Rates:
https://globalderivatives.nyx.com/sites/globalderivatives.nyx.com/files/index_margins_03172014.pdf
Eurex Spread Margin Parameters:
http://www.eurexchange.com/exchange-en/market-data/clearing-data/risk-parameters/