I believe that the sale should not be subjected to Capital Gains Tax. SPAV being engaged in the real estate business presupposes that all real estate they hold for sale are ordinary assets and therefore subject to creditable withholding tax.
I have not found any law classifying properties held by SPAVS to be capital assets.
Here is a quote from the BIR site:
"Note: Registration with the HLURB or HUDCC as a real estate dealer or developer shall be sufficient for a taxpayer to be considered as habitually engaged in the sale of real estate.
If the taxpayer is not registered with the HLURB or HUDCC as a real estate dealer or developer, he/it may nevertheless be deemed to be engaged in the real estate business through the establishment of substantial relevant evidence (such as consummation during the preceding year of at least six (6) taxable real estate sale transactions, regardless of amount; registration as habitually engaged in real estate business with the Local Government Unit or the Bureau of Internal Revenue, etc.)"
Here is a the link. It is worth the read:
www.bir.gov.ph/taxinfo/tax_capgin.htm