My next door neighbours are on Zen and their speed is fine (i tested it to compare).
No idea if they are on BTW or Zen GEA or otherwise, but I do know that they are on the older ECI Openreach fibre system and I'm on the newer Huawei system.
This was confirmed by the Openreach engineer... The thinking is that the ECI system was here first (in about 2011) but when it "filled up", the additional capacity that was added was Huawei kit, and I'm connected to that as I had to have a new FTTP install when I moved here, but it was already installed next door.
That would be very strange and unlikely, though not completely impossible.
Take what any engineer tells you with a pinch of salt. Many either don't know what they are taking about or worse they just make stuff up.
It doesn't matter if your neighbour had FTTP installed 9 years ago and you had it installed yesterday. If they were both rolled out to at the same time then you would very likely be connected to the same ECI OLT.
You and up to 32 neighbours share a single fibre that connects to a single port on a single OLT. It isn't possible to connect any of those properties to a different OLT.
It should only be possible to be on a different OLT to your neighbour if the FTTP deployments were rolled out at completely different times.
In other words FTTP was installed in half your street, up to your neighbours property and excluding your property.
Then years later Openreach came back and deployed FTTP to the rest of the street, including you.
If they were all rolled out to at the same time and became available at the same time then they are almost certainly on the same OLT.
In saying that, FTTP capacity planning wasn't the best back in the day but they still installed sufficient PON capacity for the properties around a Splitter. It would be a bit of a logistical nightmare (not to mention the availability/ordering system issues) if they had ECI, Huawei, ECI, Huawei, all next door to each other.
What speed does your neighbour subscribe to? What model of ONT do they have?
All of the FTTP from ECI OLT's have 4 port ECI ONT's and are limited to 330/50 as the ECI OLT's only have 1Gb ports coming out the back so are limited to 1Gb GEA cablelinks rather than the 10Gb you can have on Huawei/Nokia OLT's.
The 4 port Huawei ONT's are practically identical to the 4 port ECI ONT's, with only some very minor differences. The sticker on the rear will confirm the model.
If what you were told by the engineer is indeed true then that's the 1st I've come across such a scenario and you should count yourself very fortunate that the PON capacity filled up.
Especially with 80/20 FTTC available (as you said in a post recently) as that would mean either negligently low levels of FTTP capacity were installed in 2011 or your street has absolutely smashed average FTTP take up rates.