Not really. SSDP discovery uses multicast packets. These packets have a TTL field that your router should decrease, and if its value is still greater than zero AND there are multicast forwarding policies configured, forward them accordingly.
But SSDP is used only to find devices with certain capabilities... usually "normal" unicast-based protocols are used afterwards.
IMHO this issue has been fixed since then, haven't tested it yet though...
So in my understanding HE supports environments where VLANs are used, because
- the TTL of SSDP discovery messages can be set (and defaults to 2)
- the destination IP the driver connects to can be on a different subnet - HE uses its default gw to route through.
The rest is up to the end devices and the DTH.
From an other perspective, HE can have only 1 IP address, so it makes no sense to use VLAN tagging.
Actually I have Samsung speakers on an other "VLAN". Had to modify the driver slightly, but now they can be discovered and used in HE. (I had to set up igmp-proxy in my gateway). I think we can take it as a proof-of-concept... 
The switchport HE uses has to be configured to be in access mode and set to your specific (L2) VLAN id, and a DHCP server is also needed on that segment to assign the (L3) address details.
With this config, my HE (192.168.179.9) can discover and use my speakers (10.179.15.223-224). I agree with @dan.t, it's not the platform's fault...
