I was wondering if anyone has tried to use the CMMG 9mm AR magazine in a standard AR15 lower and upper using a Spikes Enhanced 9mm BCG? Are the 2 compatible at all?

I have the Spikes/Colt dedicated lower and Spikes BCG and everything works great... but I'd like to use the standard AR lower ( that's been SBR'd)  with the 9mm converted mags without purchasing the CMMG BGG and barrel...can it be done?

You mean Endomags?  Mean arms designed the 9mm insert for P-Mags and CMMG rebranded them with permission.  The Spikes bolt is cut for Glock mags so should work fine with the Endomag inserts.  I have a standard "pistol" lower that I built an upper for, using Endomags.  I use a Faxon bolt that is also cut for Glock.

To further clarify, the last time I checked CMMG only sells the Endomag version that does NOT have the built in ejector in the Endomag insert.....which is intended to be used with their RDB (Radially Delayed Blowback) setup that relies on the spring loaded ejector in the bolt like you have in 556.

While MEAN Arms sells both versions....so does Brownells and others...so if you want an Endomag that works with your Spike's straight blowback upper, then you do NOT want the CMMG 'Endomag'.

This is the mag that I have ....is this the one you're speaking of?
https://cmmginc.com/product/magazine-9-ar-conversion-30rd/

Yeah....that won't work with your Spikes straight blowback upper or any straight blowback upper since the ejector is in the lower on those.

See MEAN arms website https://www.meanarms.com/products/detail/endomag-9mm
Click on the drop down like you are going to order and notice they sell the CMMG version also...that is what you have which requires using their barrel/BCG.

See this video by mrgunsngear.
I've already confirmed with MEAN that they do indeed make the inserts for CMMG.
As he mentions in his video, I'm also not a fan of using them in straight blowbacks since you have to remember to leave the mag in the gun to clear a live round.
I'm also not a fan of any straight blowback 9mm's either.  You can see them comment on that also at the end of the video regarding how the CMMG is smoother.