The issue is not whether they declared essential patents to ETSI - it's about whether that has any significance in their licensing conversations.
Anyone can declare their IPR as essential on the ETSI database. However, ETSI clearly states that members have to establish for themselves whether the particular patents are applicable to their situation, and whether they wish to license.
ETSI's essentially provides a somewhat curated bulletin board for patent holders. They are not an enforcement agency, nor is their blessing an crucial factor in decisions made by potential licensee's IP teams.
I'd recommend speaking to CTOs and legal counsel at mid-sized firms involved in 3G/4G development (the larger ones won't speak to you unless you're managing billions). They'll give you better perspective on their licensing process.