HPHT for colour/clarity enhancement is "relatively" easy to detect and AFAIK EGL would report it if it detected it, but recently it seems that there are subtler forms of the treatment which are not so detectable. Whether EGL US or Canada is tooled up (and has the expertise) to detect them, I don't know.
My question would be "why does this stone have an EGL report?" The choice of lab is never random - so what was the person who got the report (your jeweller, his supplier, the cutter) trying to hide or emphasise? It's not cut - GIA does not grade cushions for cut. It's unlikely to be clarity - while it may or may not be a VS1, in fancy colours clarity plays a secondary role, unless the stone was so cloudy that HPHT has been used as a clarity enhancer. This leaves colour - and since you seem to feel it is intensely coloured, this may be where the rub lies.
A GIA coloured diamond report for a stone that size (1.31 or 1.51? cannot read the report) costs about $150 + shipping and a wait of two months (or about $300 and no wait). If you know the jeweller well, I would suggest that you ask him to send the stone to GIA, get it graded above any suspicion, and if it comes back within one grade (i.e. Fancy Yellow instead of Fancy Intense;) you will not return it and pay for the GIA grading and shipping. If not, he picks up the tab and gives you back all your money. If he does not cooperate, you can send the stone to GIA on your own, and if it turns out to be treated it is effectively a case of fraud which can be prosecuted through the courts... which is not a good way to end a friendship, but it does protect your wallet.