There was a session about CLEC versus ITSP (VoIP provider) at FISPA Live in Atlanta. Over the years, quite a few ISPs became ITSPs. Some of them then went on to get their CLEC license. What should you do?
8x8 is not a CLEC. RingCentral is a CLEC (at least in TX under the name RCLEC.) So there isn't really a hard and fast rule.
When deciding to get your CLEC license, there should be a business plan wrapped around it. Why do you want it?
Without a doubt, the number one reason is control. No more depending upon Level3 or other CLEC for LPN (porting numbers) and DIDs (phone numbers). As a CLEC, you can set up your infrastructure to get your own numbers from NANPA and can perform your own LNP. It's a hassle, but it is doable.
The other big reason many FISPA members are getting a CLEC license is ROW (right of way). They use ROW to put in their own fiber either buried or aerial. Building out your own fiber fits in to my Layer 1 or Layer 7 rule.
Other reasons include access to UNE in order to offer EoC, VDSL, ADSL2+ on your own gear. But then you are moving from OTT VoIP provider to network operator and VoIP provider. Other skills are required; you are relying on the ILEC for plant and repair; and you are dealing with ILEC billing.
The key is to determine why you would want the CLEC license. What does your business plan need for success?