Just email them with your registered streamyx number to check for availability. I emailed a few days ago to check for mine and there is available port!

Just a reminder, be persistent with them (no surprise there). I actually emailed about a month asking for availability and a quick reply says I'm too far from the exchange (not because there wasn't any port available). A second email sent earlier this week, the CS replied she will get back to me after consulting the respective dept for checking. The next day an email came saying there's a port available. So, even if the first reply saying you don't have it, do keep asking them as I think different CS will yield better reply (hopefully). They could also be adding more port once request are coming in and the port is full in your area (I think), so just keep asking.

One question, you can actually get speed capped at 5Mbps? I guess you have to be very persistent in asking them to up the cap in the case of speed not reaching near 4Mbps?

Its actually impossible to get to a 100% theoretical speed (at least from DSL). If let say for 4Mbps, the theoretical speed is 512KBps, the real life maximum is probably around 500KBps.

I'm quite unsure when it comes to 4Mbps to be honest but for 1Mbps of which you'll have 128KBps, you will only get around 110-115KBps.