Your subject title makes this sound like an Openreach offering but before I clicked the link I see it's api.superfastmaps.co.uk/openreach/1.1/
Any info on who 'superfastmaps' are?
WHOIS doesn't show it to be a BT thing.
Sorry to ask, but clicking unknown links is getting more risky these days 
Its owned by BT Openreach and is the location for the javascript that returns the JSON formatted status of fibre from a phone number or postcode + address.
I have written a .NET app for personal use that does checks and locate DSLAM Cabinets (for commercial projects)
https://api.superfastmaps.co.uk/openreach/1.0/ajax/check.ajax.php?input=PHONE_NUMBER&address=
or
https://api.superfastmaps.co.uk/openreach/1.0/ajax/check.ajax.php?input=POSTCODE&address=FULLADDRESS
FULLADDRESS is the same that is used on the BT Wholesale Checker, like for example (all one line):
https://api.superfastmaps.co.uk/openreach/1.0/ajax/check.ajax.php?input=ST72EY&address=FLAT 1|35 COPPER HOUSE||CREWE ROAD|ALSAGER|STOKE ON TRENT|ST7 2EY|WM|A14678662048|100010061688|100012822478
You also need to set your REFERER to https://api.superfastmaps.co.uk/openreach/1.0/
or else it will fail and return the following JSON String:
{"response":"ERROR","number":"ST72EY","message":"badreferer","referer":null}
Still has the 1 to 2 second delay, I do a similar thing for roadworks.
Paul
Edited by PaulKirby (Wed 25-Nov-15 04:23:08)