As far as I know, because of routing restrictions on the amprgw network connectivity, hosts on BGP-announced subnets of 44/8 will be unable to communicate with hosts on tunnel-routed subnets of 44/8 unless the BGP-announced subnet also runs a listed tunnel router gateway with a non-44/8 gateway address.
This is because the building-level router one hop upstream from amprgw has a fixed route directing all 44/8 traffic to amprgw. This building-level router does not speak BGP and so cannot learn about BGP-announced subnets of 44/8. This is a historical artifact; it predates the availability of BGP-announced 44/8 subnets by many years.
We hope to change this topology in the future to connectivity with the border router that DOES speak BGP, but indications are that that change will not be able to be done soon.
In the meantime, gateway tunnel routers with a non-44 gateway address (that's all of them, except HamWan's proposed gateway) are the workaround to this restriction.
I'm sorry for this difficulty but it's what we're stuck with for now. - Brian